Done. I used
cd /tmp/
wget http://rpi4.wulfy23.info/builds/rpi-4_21.02.1_1.0.7-3_r16325_extra/rpi4.64-21.02.1-27006-1.0.7-3-r16325-ext4-sys.img.gz
sysupgrade -R rpi4.64-21.02.1-27006-1.0.7-3-r16325-ext4-sys.img.gz
as rpi-sysup-online.sh -R release dropped:
flavour:release online:1.0.7-3[older] onsys:3.5.151-26
use> 'downgrade'
And now it actually works, both wifis are discoverable 
