So this just looks like the Community has to take care of the projects and/or find alternatives
Alternatives
File manager - Material Files
That one doesnt have the security vulnerability and I think it is also better. But they are pretty much equal.
Simple Gallery - Aves
I prefer Simple Gallery though, it is pretty great
Simple dialer - Welefon
Very basic, I personally use ACR phone for call recording, with disabled internet permissions. The Dev asked on Reddit about opensourcing the App and got negative responses, so maybe unlikely.
Simple Keyboard - Florisboard
Currently unmaintained but awesome. I hope it gets revived.