M1 Mini | Dell D6000 | 4 monitors working
 

Since updating to 12.1 Monterey I do seem some more quirks but it is still working as before.

I have an LG connected to Mini via HDMI
I have an ASIS monitor connected to the Dell through USB-C
I have two Viotek monitors connected to the Dell through DVI

I have to boot the Mac and login. Then I unplug the USB-C to the Dell and plug it back in. I may have to do this more than once but it does eventually find all of the monitors.

I wish there was a more scientific way to describe the plugging and unplugging of the USB-C but so far I haven't found a pattern.

Also, I have tried unloading and loading the DisplayLink software at different points but this mostly leads to the software locking up. So I leave it in the normal startup for now.

Hopefully this helps someone and if you have any thoughts on the timing of events for me - I am happy to try them out.

P.S. I don't know how to check firmware on the Dell D6000 on Mac - I didn't look really hard as it is working. But if someone wants me to check the firmware - just point in the direction of how to do this and I will post here.