I just tried out Anbox and it seems to be quite unstable for me. As using apps like Whatsapp is really needed for me I unfortunately will have to revert to Android so I will mark this question as fixed.
However, I am quite impressed with Ubuntu Touch in general, keep up the good work! Once Anbox works reliably I might get back to it.
Couple of observations:
In order to install UB I had first to revert to the original FP3 OS
link as I had installed LineageOS before
As specified on the phone page, adb and camera did not work
SMS and mobile data worked with custom APN for internet
USB connection through USB hub to phone and keyboard works
HDMI connection to a monitor did not work for me
mirscreencast through ssh works but with big latency
Anbox was quite unstable, Whatsapp booted on a black screen and Signal booted but I could not set it up
