You maybe on to something. I just checked my Kubuntu 21.04 installation and /etc/NetworkManager/NetworkManager.conf looks like this:
[main]
plugins=ifupdown,keyfile
[ifupdown]
managed=false
[device]
wifi.scan-rand-mac-address=no
I’ll try again on Manjaro KDE and try disabling MAC randomization.
thanks again for helping.
P.S. I’ll also test this on Archlinux to see if it fixes it there.