Upload a log of the failing Installation in Nanodroid thread. Then the dev could look into that.
Atm i have three theories:
- the spoofing test app is wrong (but don't really think that's the reason because in the past i used another LOS 17 gsi rom and Nanodroid hadn't any problem)
- the twrp which you use has a problem with Nanodroid
- the Nanodroid package itself has a bug which your twrp triggers
But well without logs it hard to say what exactly is the problem. Or does your twrp give more information than just error 1 in the GUI?
More than just that installation failed (Error 1) was not given in the UI indeed. Installing the Nanodroid-microG package went without error btw. Having done that, and giving app access to the Spoof package signature of microG Services core did the trick.
All seems to be running ok now.