TVHeadend + OSMC TV tuner issues

You must enable only the Sony DVB-T tuner (it seems CZ TV is only DVB-T2 which the Realtek doesn’t support.). You may have to force remove the Realtek as described here. If you haven’t read that thread then please do.

If the DVB stick stayed powered (soft reboot or leaving the hub powered) it would not be re-initialized fully. Try powering off completely, including the hub, then turn everything on again.

Unfortunately, that’s what happens. Only a cold re-boot will start everything up in the right order.