@cristicc It is the copy/paste _from_ geany that doesn't work for me in geany 3.18 on gtk3.24.31 (on F36 gnome/wayland) using the middle mouse button. I think it hasn't worked for a couple of years (did it ever work?) It's a pain on a trackpad anyway, so it didn't register as a big loss.
I think both CTRL-C/V copy/paste as well as middle-mouse-button _into_ geany have worked quite consistently on various combinations.