I wonder if I could use m3u stream of a provider to override the same(weak) channel provided by HDHR and retain the guide data, etc ....
This would also save tuners on HDHR
Yes, you can. Assuming, of course, that you have a valid link to a stream of the channel you're trying to override.
For additional information on this topic, the posts regarding channel remapping will probably help you best. Just search for "remap".
I don't want to remap. I want to override which I believe is different.
I am trying to override channel 45.1 but it doesn't work so I have put for now 145.1 but it doesn't get EPG. The guide art is also missing from channels program guide so I would like to override that too.
Yes they're different on the surface, but the methodology is the same. Instead of using a higher priority Custom Channel to point to a stream from Channels on a different number, change the stream to use your internet-based stream of the local channel. The tips for using the stationID in the tvc-guide-stationid tag will take care of the guide data and station logo/name.
I was directing you to those threads to give you a starting point for how to achieve your goals, since the groundwork had already been done.
Edit: I see you edited your post to include which station you are trying to access. If you have a TVE source setup in Channels, that station is available on channel 6756.
There is problem with finding the tvc-guide-stationid is the station did not provide a logo so a generic one is used on zap2it ;(
https://zap2it.tmsimg.com/sources/generic/generic_sources_h3.png
EDIT: Found it in a blob of json used to populate the grid on zap2it - 98229
I can get guide data for the M3U channel, however I can not override the HDHR channel so I have to use a different channel number - 145.1 in order for the channel to show up in guide or be watched. I believe this is a bug. OTA channels coming from HDHR can not be overridden ;(
EDIT: I could probably disable the channel on HDHR but I would rather not do that.
EDIT2: The source priority setting seems bogus.
Here is the final(?) version. I have to keep 100 added to the channel numbers from HDHR. The urls are from each broadcaster website so they are legit.
Program guide can be added from OTA in zip 95050
#EXTM3U
#EXTINF:-1 channel-id="136.3" tvg-chno="136.3" tvg-logo="https://tmsimg.fancybits.co/assets/s67818_ll_h15_aa.png?w=360&h=270" tvc-guide-stationid="67818" tvg-name="KICUDT3" group-title="SD",CGTN
https://live.cgtn.com/1000/prog_index.m3u8
#EXTINF:-1 channel-id="145.1" tvg-chno="145.1" tvg-logo="http://thedovevod.tulix.tv/vod/images/livestream.jpg" tvc-guide-art="http://thedovevod.tulix.tv/vod/images/livestream.jpg" tvc-guide-stationid="98229" tvg-name="KQROLD" group-title="HD",KQRO-LD
http://rrsatrtmp.tulix.tv/thedove/thedove.smil/playlist.m3u8
#EXTINF:-1 channel-id="145.2" tvg-chno="145.2" tvg-logo="https://tmsimg.fancybits.co/assets/s106796_ll_h15_aa.png?w=360&h=270" tvc-guide-stationid="98237" tvg-name="KQROLD2" group-title="HD",CMCUSA
http://cmctv.ios.internapcdn.net/cmctv_vitalstream_com/live_1/CMCU-92/playlist.m3u8
#EXTINF:-1 channel-id="145.3" tvg-chno="145.3" tvg-logo="https://tmsimg.fancybits.co/assets/s91404_ll_h15_ab.png?w=360&h=270" tvc-guide-stationid="98239" tvg-name="KQROLD3" group-title="HD",CMC
http://amg01441-cmctv-cmctv-ono-gk05v.amagi.tv/playlist1080_p.m3u8
#EXTINF:-1 channel-id="145.4" tvg-chno="145.4" tvg-logo="https://ginikofaith.com/channels/logo/kqsl-8.jpg" tvc-guide-art="https://ginikofaith.com/channels/logo/kqsl-8.jpg" tvc-guide-stationid="98267" tvg-name="KQROLD4" group-title="HD",KQSL
http://uni01rtmp.tulix.tv/kqsltv/kqsltv/playlist.m3u8
#EXTINF:-1 channel-id="160.4" tvg-chno="160.4" tvg-logo="https://tmsimg.fancybits.co/assets/s86894_ll_h15_aa.png?w=360&h=270" tvc-guide-stationid="109636" tvg-name="KPJKDT4" group-title="HD",DEUWELL
http://dwamdstream102.akamaized.net/hls/live/2015525/dwstream102/stream05/streamPlaylist.m3u8The source priority setting seems bogus.
Are you changing the source priority on your client device or just the server? If you set it to the same channel number and have it set to higher priority on the client device, it should use the custom channel stream. I’m pretty sure I have done this before.
Setting priority higher for the M3U source on both server and ATV but it doesn't take.
It seems HDHR channel numbers have simply higher priority which contradicts https://getchannels.com/docs/channels-dvr-server/how-to/custom-channels/
Note: Be sure not to use a channel number that exists in another source’s lineup. Channels will merge them together and use the prioritized channel.
I disabled the local PBS station and used a m3u stream with the same channel-number set to the local number 8.1 .
Would help if you mentioned where 
If on HDHR I already said I am not super excited about this option.
What part is not working when you have two stations with the same number?
Where exactly are you playing from and what happens when you do?
At this point I am not sure if this is worth having. I was trying to override an HDHR channel with M3U source. Adding 100 to the channel number is an acceptable option for me.