There's a list of publicly available IPTV channels here

https://github.com/iptv-org/iptv

It's a big list which you can filter and export if you find something you like.

https://iptv-org.github.io/

I haven't tried in a while so YMMV.

I've been looking at installing Dispatcherr recently. Not positive it will solve all of your problems, but might help with management? I haven't installed it yet, so I'm not 100%. https://github.com/Dispatcharr/Dispatcharr

I've found even harder to find than live sports are live TV premium channels for shows. All my previous places I used to go to are either not working anymore, paid, or only work in browser with a good adblocker. Lmk if you find a suitable solution

Have a look at FMHY

You can get an antenna and an HDHomerun box if the teams you want are broadcast in your area.

One of the things you can do is get a proper iptv provider. However most of them have literally thousands of channels that are entirely irrelevant to what you want and also Jellyfin will choke on having that many channels added (ask me how I know).

One of the things you can do is use Dispatcharr to manage your iptv channels and act as a middleman. You can do things like only add channels from the sports group to it and that will give you a manageable number of channels to pass to Jellyfin. You can also experiment with other tools that you can find in the Dispatcharr Discord to do things like automatically create a list of all of today's sports events, create channels automatically for each event, create a group of all the games for today's NFL games, etc... Dispatcharr will provide an m3u file you can give to Jellyfin.

I compiled my m3u playlist by searching through various lists, especially iptv-org linked on another comment.

As far as sports, I've found a variety of random sports channels but nothing targeted to my area/teams.

I think it could be difficult to find reliable and relevant sports channels that are more legal/stable. Like someone else said, you might want an antenna for local sports if you don't already have.

There is a reddit channel that points various sources of video, something eye pee tee vee new zone.

If you want premium channels, you likely wont find that for free. You can get cheap iptv from online stores for a few bucks a month. I dont recommend the ones that have their own website, as they markup the price a lot for the same service that you can find on online storefronts like g2a or z2u. They are resellers, but its a good first step until you can find a private provider which will give higher quality streams and better epg. I also recommend dispatcharr like a lot of other comments was saying, that will allow you to easily connect it to jellyfin in a format it understands. Oh and if you go the z2u route, ask for a trial before you buy, all good resellers will give you a free trial that last from 8 hrs to 24hrs to see what channels they have and verify the stream quality. Lmk if you have any questions.