Follow-up. I found another epg, unfortunately also without LNC tags. I see program information on EPG on Apple TV client, but I cannot record 
You need the beta for xmltv recording functionality.
But i am on beta. I updated server with shift pressed.
Is there any XMLTV rules that Channels enforce to proper working? for example channel id must be without spaces?
You need the beta app on your Apple TV
Where can I apply for beta access in testflight?
That still not explain why on server I see blank rows in guide, tough
getchannels.com/beta is used for TestFlight access
I'm guessing your xmltv file is using some character encoding which is not working. Please email the xmltv file to [email protected] and also click Help > Submit Diagnostics on the DVR web UI.
Ok I sent the logs, and try to test beta version 
In the logs its showing no channel mappings, usually this happens because the lcn tags are missing.
2020/04/12 13:19:13.898688 [DVR] Fetched guide data for XMLTV-CUSTOM in 0s
2020/04/12 13:19:13.918591 [DVR] Indexed 0 airings (0 channels) [0s index]
Can you click the pencil icon under your HDHR, then click pencil icon on the right side of a channel and screenshot what is shown.
That doesn't look right. Does the HDHR Connect have XMLTV assigned to it?
yes but I cannot make assignment now, I don't see "edit" option 
wtf
Should I delete xmltv source and try again? or maybe delete HDHomerun and try to re-add it? I put it on my hosting here
I'm not sure what you did. When I add the xmltv here on my HDHR it shows the picker and lets me assign channels.
I had previously something similar. Now I re-added HDHomeRun, re-scan channels. Now I see something like this
Started to associate channels (exept tvp3 which i dont have listing for )
Re-scanned xmltv source
and this is the result,
my mind is blowing up
i have only that... Ok, now we're getting into something. I switch to https://epg-polska.net/guide.xml
and I have the same list of channels. I see this because I have only TVP3 Poznan. So is this possible that this new link is not accepted at all because the old one is still cached somehow?
Neither of the xmltv files you linked has that channel, so I'm not sure where that's coming from. Did you try another different xmltv too?
I probably had one generated by WebGrab+Plus but since that app requires 1GB dependency of MonoDevelop I deleted that.But I can confirm that https://epg-polska.net/guide.xml entered in browser take long time to load...so maybe it is some timeout issue as channels is not available to get the data.
If there is a timeout issue it will say timeout in the logs.
My recent logs:
2020/04/13 23:38:20.941564 [IDX] Pruned 0 expired groups from XMLTV-CUSTOM in 334.539µs.
2020/04/13 23:38:20.942180 [IDX] Pruned 0 expired groups from X-TVE in 580.313µs.
2020/04/13 23:38:20.947726 [IDX] Pruned 0 expired airings from XMLTV-CUSTOM in 102.145µs.
2020/04/13 23:38:21.004008 [IDX] Pruned 34 expired airings from X-TVE in 56.233771ms.
2020/04/13 23:38:23.507340 [DVR] Waiting 21m36.492663s until next job 1586815200-11 Magnum, P.I.
2020/04/13 23:42:35.402815 [IDX] Pruned 0 expired groups from XMLTV-CUSTOM in 2.851409ms.
2020/04/13 23:42:35.402977 [IDX] Pruned 0 expired groups from X-TVE in 122.843µs.
2020/04/13 23:42:35.407672 [IDX] Pruned 0 expired airings from XMLTV-CUSTOM in 128.32µs.
2020/04/13 23:42:35.658710 [IDX] Pruned 1 expired airings from X-TVE in 250.951631ms.
2020/04/13 23:42:40.514289 [DVR] Waiting 17m19.485715s until next job 1586815200-11 Magnum, P.I.
2020/04/13 23:42:52.096970 [IDX] Pruned 0 expired groups from XMLTV-CUSTOM in 53.249µs.
2020/04/13 23:42:52.097218 [IDX] Pruned 0 expired groups from X-TVE in 179.178µs.
2020/04/13 23:42:52.099384 [IDX] Pruned 0 expired airings from XMLTV-CUSTOM in 58.818µs.
2020/04/13 23:42:52.099868 [IDX] Pruned 0 expired airings from X-TVE in 410.713µs.
2020/04/13 23:42:54.255962 [DVR] Waiting 17m5.744041s until next job 1586815200-11 Magnum, P.I.
Never heard that XML content protection is possible, but when I download that xml file from the site and put it on my server I cannot assign channels to numbers.I'm out of options.
Let's call it a day. I'm terrible sorry that I wasted so much of your time on Easter Monday, I appreciate patience.
Looks that Poland belong to authoritarian countries and government prevent us from watching TV non-standard way so it never work with Channels. Pity as I won't renew subscription. Have a nice afternoon
This is crazy - I launched today CHannels client on Apple TV and the EPG data was there despite I cleared guide service on server...when I launched Channels Beta it was not there so I assume it's caching issue.