Hi, i’m quiet a user like you, on board since jolla 1 but without coding experience and i tried myself to make microg work lately. Not shure if this is helpful:
Go to Jolla Settings App > Android Support > Second Tick Box should be activated, something like “Deactivate Checking of Android Support Package”. This should allow inofficial Stuff to run like Signature Spoofing, at least it worked for me.
At your own risk and good Luck!