I think Astra UHD will be hevc and I don't think you'll be able to play that with your hardware spec.
In theory you should see something - there was an issue with kodi that made hevc transport streams fail but other file formats work. I don't know what release version you need for the fix.
When you say "UHD from file no problem" it doesn't mean broadcast will work - the file that works may be low bitrate hevc or maybe h264 (in which case your GPU will decode it). You need something very recent GPU/CPU/APU wise to get hardware hevc decode and for broadcast bitrates most CPUs just won't be fast enough to decode in software.
I don't know what the situation is with tvheadend + UHD sat - I assume you can record and try to play the transport stream if tvheadend is setup to record like that.