A trivial fix to help those that have rebuilt their kernels, and to improve robustness. A change to /etc/init.d/mythtv-backend is required to check for the existence of /proc/sys/dev/rtc/max-user-freq before trying to write "1024" to it.
AAt least in kernel 18.104.22.168, the RTC emulation by the new HPET facility does not extend to putting a fake entry to match the old RTC in /proc/sys/dev
Instead, you have to use
echo 1024 >/proc/sys/dev/hpet/max-user-freq
The start script should check for the existence of both rte and hpet before it tries to write to them. Because it does not, if the write fails the script fails completely (ie mythbackend does not start).
If this script is within the scope of LMCE (if not whose it is?) I am happy to code this and would like to get some help on how to get a patch generated once I've changed the script, and how to submit it for inclusion to LMCE.