Other solutions suggested "use a cable" 
I now also tried the latest LE 12 nightly which should with a more recent kernel than 6.6.78 - but no luck. invalid key error still is their with the router being two meters away...maybe it also fails if the signal is too good?
Will try LE13 nightly next to see if this supports wifi.
And from what it looks like it seems to be a pure software problem/bug? The same PI SBC has no problems with the same wifi/router when running PiOS for example.
Hello everyone!
introduced in LE 10/11(?) the "invalid key" problem (broken wifi) seems still to be a problem in LE 12.I searched the forum/githubs/reddits/internet and as of today plenty of people seem to have problems.
Many work'a'rounds with scripts or other tweaks (disabling 802.11n etc.)
Most interesting seems the comment from @helmat in this issue here:
claiming that the kernel 6.6.78 actually might fixes things...
but at the moment (stable) LE 12.0.2 only ships 6.6.71 (RPi2-5 6.6.70)...
