Not free, but quite good sales on fps games on gog.com right now:
https://www.gog.com/en/game/deus_ex_human_revolution_directors_cut
https://www.gog.com/en/game/bioshock_remastered
https://www.gog.com/en/game/bioshock_infinite
https://www.gog.com/en/game/the_outer_worlds_spacers_choice_edition
https://www.gog.com/en/game/fallout_4_game_of_the_year_edition
https://www.gog.com/en/game/fallout_3_game_of_the_year_edition
https://www.gog.com/en/game/fallout_new_vegas_ultimate_edition
https://www.gog.com/en/game/metro_franchise_bundle

Personally I really enjoyed Deus Ex: Human Revolution, the Outer Worlds and Fallout New Vegas. The others aren't bad either but those three are my favourites in the list.

Deadlock. Lots of communication, if you have a good team. Third person shooter MOBA w/ heavy moderation (people actualy get comm banned for being shitty). Will have to go to the discussion page in steam and get an invite tho.

...it's wild that it's one of the most played games on steam and still needs an invite. -_-

If you want comms, you need teamplay.

If you want teamplay you go milsim.

I’ve been playing a bit of Arma Reforger lately. Played a bunch of Squad in the past.

Squad has its comms organised better.

Most classic roguelikes are free and many even open source. It is a great genre and if you take time to learn one of them you'll be at home in any. They are all played in micro-turns so time only advances when you make inputs. That means you can get up at any time without having to pause the game. They have many other features mostly unique to them, too. For instance, in basically all of them everything stays the way you leave it. Items on the ground don't despawn after a while. Monsters can also pick up and use your items, though.

Cataclysm: Dark Days Ahead is one of my favorite games of all time. You can explore realistic towns and forests after the apocalypse. For instance, you can find most of the items that would be in a real kitchen in an in-game kitchen and use them to craft a staggering amount of stuff. While you'll mostly see zombie variants, there are enough different horrifying things to encounter that every run is different.

The controls of C:DDA are numerous, though. It may not be a friendly starting point if you have no experience with anything like it. I'm not sure what to recommend for that. Brogue is easy to get into but pretty shallow. Dungeon Crawl: Stone Soup might be a decent introduction to the genre.

If you have MCC on Steam, I recommend Ruby's Rebalanced Mod for Halo: CE. As a life long Halo player, it felt like a breath of fresh air and reminded me of how I first felt playing it almost 25 years ago.

Or just do what I do and play DOOM and DOOM II every week lol.

In addition to free game suggestions, I would suggest periodically checking gg.deals to get commercial games at significant discounts. It aggregates discounts from different platforms when games go on sale.

If you don't mind having an Epic Games Store account, you can also claim the weekly free games from there.

If you own Quake, the Quake Brutalist Jam 3 is a lot of fun and many hours of content. It works off a new set of weapons/enemies so it’s not just “more Quake”, though obviously works within that mold.

Have you heard what people are like with open mics? Time to n-word was like 3 seconds last time I tried turning it on in a game. If you want communication, you'll probably have to party up with some people you know or otherwise met via Discord who are also looking to party up.

Hmm. Free is harder.

I've been on a Soulash 2 kick lately. It's like dwarf fortress adventure mode. Very roguelike, single player.

Songs of Syx is a city-state simulator. Pretty much the best parts of SimCity, rimworld, and Total War mixed together.

Project silverfish is an extraction shooter that I think most fits the title of STALKER spiritual successor.

Beyond All Reason, mentioned elsewhere, is the best RTS around right now. Completely free.

Factorio/Dyson sphere program for factory games.

Sorry, not a lot of free recommendations.

I don't really have any free games to suggest, other than Manic Miners on itch which is fantastic if a little short.

I just got Queen's Domain the other day because I played the demo earlier this year and was hooked. It's a slow-paced dungeon crawler in the likes of King's Field, Lunacid, Verho, and FlyKnight where you play as the prince of a royal family on a mission to find out what happened to your dad the king, and possibly put an end to an evil cataclysm that's building up. It takes place on a small island chain with tons of twisting paths, hidden corners and secrets, puzzles, challenges, and crazy enemies. The graphics and art style have a retro look and feel to them, and it's just incredibly fun.

Tainted Grail is also really fun as a super-indie "Elder Scrolls-like." It follows a version of Arthurian legend, taking place in Avalon wrapped in a magical apocalypse where the Wyrdness (basically a physical manifestation of magic that feeds on every sentient beings thoughts and can make whatever they dream/nightmare, and no one has any control over it). Plus there's a major DLC (along with all the other FREE DLC they've been releasing) called Sanctuary of Sarras that takes place on the bottom of the ocean, and everything is all Old-Ones and Eldritch themed. I'm playing through that one right now too and absolutely loving it. The vibes in the DLC are absolutely immaculate if you're into underwater horror and such.

How about UZDoom and some kick-ass famous WADs from Cacowards from all the years? Freedoom wads let you do a lot of it without owning the original games:

• https://doomwiki.org/wiki/IWAD

Easily one of the most bountiful communities with endless maps and mods and sprites and music and whatever you can imagine and then some.

DDNet

Warframe

Classic DOOM has best Linux support of all games in my opinion. Because it was opensourced and plenty of great community-maintained source ports.

Doom has tons of amazing community-made content (WADs) made within last 30 years. Like what other games have mods that feature whole original soundtracks? It also has pretty competitive speedrunning and multiplayer scene. And some very, very difficult levels.

So to play the game you need port and also IWAD files containing levels, textures, etc. Official iwads are not free. So your options are

1. Buy D1+D2 on steam/gog, grab the iwads, ignore official source port and go play much better community ones
2. Pirate the iwads. Extremely easy, the files didn't change since the 90s and have been shared all over the Internet.
3. First episode of D1 is free. Search for Doom Shareware. It's packaged in some distros even.
4. Use the community-made iwad replacements from freedoom project. These are completely foss and also the website has some source port recommendations so probably start with them. I myself started playing DOOM with freedoom :)

Free games? The itch.io Halloween sale is on and I did a post with like 130 of them yesterday, and that's just the ones I hadn't already claimed! Most of them are probably terrible, but think of sifting through the haystack as a kind of metagame in itself.

Try 7DaysToDie, it has multiplayer the way you want, with necessary talking. And is like minecraft but realistic.

Playing with yourself is free, and almost everyone loves it.

Give that a go.

story games works too

Its not even close to anything else you talked about, but vivid/stasis is amazing

Free is obviously a big limitation. Honestly, I feel like the only free game I can actually recommend at this point is Dota 2, although notably you really need someone to tutor you to get into the game. Its just too complex, too team-focused, and too deep to get into without a more experienced player to guide you. That said, if you do get through the hundreds of hours of learning, there really is nothing else that compares.

Outside of this, now that Steam is pushing developers to make demos again, try giving some of them a shot. Its a fun way to get a sampling platter of hundreds of different games, especially during Steam's festivals. If you enjoy it enough, you can always buy the full game later.

Surprised you haven’t played Overwatch! I’m loving it

Ffxiv play up to shadowbringers for free. Im 300 hours in and STILL havent hit that point.

Find the Needle is close to release. Demo is quite fun. Just install and play via Steam. Works great under default proton, no interaction or settings needed there.

The free games I play the most are marvel snap card game and chess

Dark Messiah of Might and Magic: has a nice melee combat and strong spells, but try some mods to make it harder like this that is made in linux

Selaco is a fun little shooter, it does cost some money tho.

Dark Mod

Not free, but Planetcrafter is fantastic of you like exploring and changing environments.

Sheepy: A short adventure: https://store.steampowered.com/app/1568400/Sheepy_A_Short_Adventure/

Sniper Elite 5 or aion.

xonotic is free, open source and runs natively on linux. fast arena fps, no wine needed. not an fps, but i also made a free browser game called salvage.run if you want something short between matches

Have you looked through the games section of your software app?

Overwatch

If you’re committing solely to video games, it looks like you already know what you want.

There’s so many good solo board games out there.

And so much to read.

My backlog goes on for millennia.