Provide (old) F-Droid and other open source software for old Android versions

What did you do? (clear steps if possible)

Trying to install F-Droid and other open source software on an Android 4 based device which no longer receives updates from the manufacturer

What did you expect to see?

Being able to use F-Droid and other open source software on an Android 4 based device to prolong its lifetime beyond what commercial vendors support (even if it means to use older versions of apps)

What did you see instead?

Impossible to use the device, essentially turning it into e-waste