I'm surprised to hear this. Fortunately it doesn't look like the source code itself got taken over [1], and of course F-Droid, which is always the best place to get any open source Android application, still has the same version as the latest Github release. [2]

These applications are blessedly feature complete, and I haven't noticed any issues being "stuck" on the F-Droid versions.

[1] https://github.com/SimpleMobileTools/Simple-File-Manager

[2] https://f-droid.org/en/packages/com.simplemobiletools.filema...