Topic: UFX by firewire Big Sur driver (?) issue

Help, comments, explanations and suggestions on the rather long winded below most welcome.
My UFX happily works via a Firewire connection to the Apple display which is, through a TB3 to TB2 connector, connected to my iMacPro running Catalina.
I updated to Big Sur early this year and TotalMix worked, however as my MOTU MIDI device (using a USB connection) didn’t I backed out of the update and remained on Catalina using the previouslyused UFX drivers until MOTU released drivers for Big Sur.
So in July I again updated to Big Sur, reinstalled the RME driver which appeared to work (ie the screen displayed) and then the MOTU Big Sur compatible driver. The MOTU worked but my UFX didn’t after the reboot for installing the MOTU driver; Totalmix reported no devices. Backed out to Catalina again.
Yesterday I tried updating to Big Sur again and following doing so spent the rest of the day and today following the advice on this forum on using boot into recovery mode and running kmutil and re-permitting drivers without any success. I did this a number of times and noted that sometimes the UFX driver would be there asking for permission to load. But wouldn’t on rebooting, other times it wasn’t there. So I would reinstall- sometimes being asked to permit in Security and Priacy other times not being asked.
All of which leads me to ask: does anyone have any suggestions as why repeating the same process exactly numerous times led to different outcomes? Slightly different timings in rebooting, as that was being driven by me, I could understand for the lack of a Security and Privacy notification, but when rerunning the installer and only sometimes getting a Security and Privacy approval request I don’t.
So my final questions:
1. Anyone successfully running a UFX via Firewire on an iMacPro with Big Sur? If so how did you install ?
2. Same but via a USB connection. And if so the USB connect path.