I haven’t tried Sync-in but if simple is what you want then a Synology DS225+ should get you up n running quickly.
https://www.androidpolice.com/synology-as-a-google-drive-alternative/

Which part of the seafile install was it that made you back off?
https://manual.seafile.com/latest/setup/setup_ce_by_docker/

Lutris is impressive when it comes to game launchers and RAM efficiency, especially when compared to the ones using Electron.

That was an interesting read.

If you wanna own your audiobooks you might wanna check out https://libro.fm/ - they allow you to download the bought audiobook without drm.
I gladly accept tips for similar sites when it comes to buying ebooks.