Enable monitor mode, bcm4355c0 Pi4 5.10.92-v7l+

[54926]

root@raspberrypi:/home/pi/nexmon/patches/bcm43455c0/7_45_189/nexmon_csi/utils/makecsiparams# iw phy iw dev wlan0 info | gawk '/wiphy/ {printf "phy" $2}' interface add mon0 type monitor
command failed: Operation not supported (-95)

root@raspberrypi:/home/pi# iw dev
phy#0
Interface mon0
ifindex 4
wdev 0x2

	type monitor
	channel 157 (5785 MHz), width: 80 MHz, center1: 5775 MHz
	txpower 31.00 dBm
Interface wlan0
	ifindex 3
	wdev 0x1

	type managed
	channel 157 (5785 MHz), width: 80 MHz, center1: 5775 MHz
	txpower 31.00 dBm

how to solve it, thank you to everyone who provided help.

[zeroby0]

Restart the Pi and try again? It's the fastest and most reliable 'fix' for me.

[Hamzu24]

sudo iw dev mon0 del
Fixes it for me