OK, I got a new kernel built (18.104.22.168) and installed, along with the latext nvidia drivers (177.80) and latest V4L-DVB drivers.
My DVB tuners seem MUCH more stable, and most LMCE things seem to work, will know more over the next few days.
/proc/dev/sys/rtc disappeared though which meant manually editing the mythtv-backend start script to get rid of where it tries to write to it. HPET (high precision timer) is supposed to create the rtc directory but it doesn't, though enabled in my kernel build.
Anyway, my MCE remote has stopped working. I get the message box in the UI telling me that mce_usb2 is installed when I plug it in, and the MD has a device defined, but the remote has no effect. Any ideas where to start troubleshooting?