I think they are very good. Don't expect any fancy features though. The gallery for example only shows pictures in directories and has very basic editing capabilities. There is no album management or automatic backup of any sort.
Hi,
having an Android phone as secondary, I would say:
best would be a custom rom like grapheneos (Pixel only), lineageos or e/os. They come with plenty alternative apps from the getgo.
Most Fossify apps are on F-Droid. They used to be known under the name “Simple Mobile Tools” and presented with orange app icons. The original author sold their brand/their userbase to an adware company, but the project lives on in form of this community-driven fork.