[Ubuntu 18.04] Scatter doesn't connect to any dapp - neither with Firefox nor Chromium

[mschoenebeck]

I'm using scatter 11.0.0 AppImage since version 12.1.1 seems to be not functional on Ubuntu (when I open it there is no Icon neither in the system tray nor in the app bar; it's not being recognized by any app as well). However, I use scatter since the beginning and it always kinda worked (at least with Chrome, with Firefox only some dapps). Now it completely stopped working at all. No dapp recognizes my scatter running in the background. Is there any fix to this? What can I do to make it work again?