[ABC123]

MacBook Air M1 2020
Monterey 12.3.1
DisplayLink Manager 1.6.1 Build 59.135

Targus DOCK120AP with own power supply
MBA M1 plugged in using 30W adaptor

Old set up was
Dell P2319H (1) using HDMI to HDMI
Dell P2319H (2) using DVI to HDMI

I've managed to get dual set up working again by changing monitor 2 to DP to DP cabling

Switching the cabling above for some reason caused unstable signal on monitor 1 (DP DP)

Things tried (no order)
- Downgrade to Big Sur
- DisplayLink old installs (1.5, 1.6 versions etc.)
- Delete HD and clean install of OS (realise not an option for all)
- Power cable pull tricks etc
- NVRAM / SMC resets
- Validated monitor working, cabling working etc.
- Deleting com.apple.windowserver.plist

Odd things found
- When stopped working initially, issue was monitor 2 not receiving HDMI signal
- Inverting cabling so monitor 2 was HDMI to HDMI didn't help
- A 'simple' single HDMI external monitor via USB-C hub didn't work but did work on a smart TV
- After clean OS install the issue appeared to be active monitor (could move mouse onto it / lose windows over there) but screen all black (monitor did not report no signal)

I've made Apple well aware of the issue and the discussions online (to extent that helps anything right now)

The inconsistency (it stopped working after it went to sleep but now it works again) of course points to OS...