In the nightly tarball I can not confirm 1 and 2, so 1 and 2 seem to be solved.
Is that with or without the changes of https://github.com/geany/geany/issues/3271#issuecomment-1236382367?
I doubt that the plugins will have any effect.
Geany by PPA was also built yesterday
Thanks to @xiota, but please keep using the Geany made from the tarball, you can make changes to that.
Because of that, I think that not Scintilla is the problem, but Geany, but maybe I'm wrong.
What do you think about that?
To be clear, the whole display of the edit window is Scintilla control, its unlikely it will be anything Geany did, initial focus is just passed to Scintilla, so if it is in fact having an effect it will still be in Scintilla. Do pass _all_ the observations you have made above on to Scintilla though, as I said before anything you can provide to help may make it easier to narrow down the cause or make it easier for Neil to reproduce the problem.
@ralf3u thanks again for your effort here, since nobody else with Geany has managed to reproduce it with the current GIt (or they are not saying so) there is not much we can do to help, and its up to you to help Neil.