I use Syncthing for files/photos/videos and Nextcloud for calendar and contacts.

My method is much more manual and involved, but fits my needs:

I have my pictures, documents, and music folders synced automatically to a few computers via Syncthing. At the start op each month, I export my contacts, Obtainium apps, and other files to my documents. At this time, I also make backups to the cloud and make a couple copies to external hard drives. It may sound intensive, but it only takes 5 minutes a month.

I restart / update my phone very often for various tests and projects. Whenever I need to do so, I upload these files from my computer or hard drive. Using a guide that I've made myself, it takes maybe ten minutes to have my phone exactly the way it was before.

A lot of FOSS apps come with an 'export' or 'backup' options. I have a folder called Backup where I keep any app backup I need and use Syncthing to sync the backup folder to my PC. I also use Syncthing to sync my media folders and everything else to my PC.

I'm on GrapheneOS so I use the builtin seedvault backups. They kind of suck but they mostly work.

I run a synology nas, and use their photo system. Occasionally I'll run thru critical apps (med schedule/dosing/refill reminder, blood pressure logs, signal...) and make backups, then stick them/update them in a folder on the nas, etc.

Basically anything I want to keep, goes on the nas. What's on my phone is just temporary, and disposable.

For stuff like calendar and contacts, I run radicale and then sync it via DAVx5, then use Fossify Calendar and such. I moved away from G 8 years ago, and the only link is my yt channel (meh, disposable), nest (smoke alarms and thermostat), and store credit card (for buying devices). Calendar, contacts, tasks, notes, drive, photos, etc are all handled by the nas; email is through my hosting provider.

And while I'd like to roll my own hardware for a nas, the synology system is pretty forgiving to new users, and while I think I can do it, it'd be more work and more monitoring, so I'm staying put until something lights a fire under me.

For photos and videos, Immich. I don't really care about backups for contacts, messages, or games, so I just do photos and videos.

Look at swiftbackup it's great

I use that and immich

You learn to handle a lot of your data yourself to degoogle. Do a physical backup to a USB flash drive.

I use grapheneos and Seedvault somewhat works. But for the most part I use the build in backup mechanism of the app. Then I select nextcloud as the target for the backups. So in case I loose the device all my backup files are safe on my nextcloud instance. And for fotos specifically I use immich.

i just use rsync to sync some folders, sms/contacts/calllog backup tool from fdroid to periodically dump them to a folder, and titanium backup for some apps

I use Neo Backup. It allows backing up APKs and app data. You need root for it though.

If you want to get your backup off your device you can just use ADB with it, or something like Syncthing (though depending on how many apps you have, the backup can be pretty massive).