I am struggling with the same problem here using a Hauppauge dual DVB-T2 stick connected to Hardkernel N2.
Meanwhile it’s 9.2.3. If I enable “latest drivers from kernel” the driver (?) crashes. System works but tvheadend server (4.2) doesn’t. No web interface, no connection from clients possible. Without driver add-ons it works, but without the second receiver of the Hauppauge stick.
If I shall provide logs I am ready to do.
More information are available in this thread: CoreELEC 9.2.3: tvheadend not working
With the help of Ray I found out that it seems to be the same problem as discussed here.