As far as I know, the app store version of tvheadend is still broken. Refer to this thread and follow HarryL’s instructions with a fresh install of osmc.
The important thing (for me, anyway) was not to install the app store version at all. It didn’t work if I tried removing and reinstalling. Start from scratch. There is no guarantee that this will work, since you are using a different tuner, but it might help. If you have any questions about your particular tuner drivers, that linked thread would probably be a good place to ask.