Tvheadend

The key to setting up Freesat is to tune in to 11428H (ie play the mux with something like VLC) - you won't see anything but will get the lists of muxes services and bouquets.

Would that be :

Frequency : 11428
Polarization : H
Sym rate : 27500

If that's it then it's not in the built-in muxes list, but I did add it manually and I tried playing it, I just get an error in VLC, it fails. It also shows as FAIL in tvheadend.
Log from tvheadend :

2021-03-08 15:15:49.552 [   INFO] subscription: 0480: "HTTP" unsubscribing, hostname="172.21.2.2", client="VLC/3.0.11 LibVLC/3.0.11" 
2021-03-08 15:15:49.568 [   INFO] http: 172.21.2.2: using ticket ad70df9e617967fd901e2b58c13bd3df5989b73d for /stream/mux/3473db7e9793bb1146b55e248dfeb939
2021-03-08 15:15:49.568 [   INFO] mpegts: 11428H in Freesat - tuning on SAT>IP DVB-S Tuner #2 (172.21.3.175@UDP)
2021-03-08 15:15:49.568 [   INFO] subscription: 0484: "HTTP" subscribing to mux "11428H", weight: 10, adapter: "SAT>IP DVB-S Tuner #2 (172.21.3.175@UDP)", network: "Freesat", service: "Raw PID Subscription", hostname="172.21.2.2", client="VLC/3.0.11 LibVLC/3.0.11" 
2021-03-08 15:15:59.568 [WARNING] subscription: 0484: service instance is bad, reason: No input detected

Your input can't be opened:
VLC is unable to open the MRL 'http://172.22.1.22:9981/stream/mux/3473db7e9793bb1146b55e248dfeb939?ticket=ad70df9e617967fd901e2b58c13bd3df5989b73d'. Check the log for details.

These settings work for me, however some descriptions have the mux frequency as 11425 so maybe that's something else to try.

Noticed that linuxserver/tvheadend:latest is actually still a 3.2 version, so I just upgraded to 4.2. I'm finding a lot more stuff, but most of the new ones aren't working, things like Sky Cinema which is showing unencrypted but I assume is encrypted.

I tried your settings exactly with the new version and still getting the same result.
I tried 11425 and let it play for a while, it did find 40 services but almost all of them are encrypted and none of them look like Freesat channels. I wonder what's wrong, should I let 11425 play in vlc for a while or is that just wasting time ?

It should only take a few minutes to capture the muxes.

Re Tvheadend version, the recommendation now is to use the latest development version 4.3, which will hopefully become release 4.4 before too long. I can't guarantee that will fix your problem though...

Right, unfortunately they don't seem to have a container for that version yet, the latest I can see is 4.2.8.
Guess I'll keep fiddling with it, maybe I'll figure something out, thanks

Any chance my problem is with the SAT->IP's positions ?
I just assumed I should turn them all on, but looking at the doc apparently those are meant to select the dish, so I probably shouldn't. Is there a way to know which one(s) I should be using on each tuner for a digibit twin ?
This might explain why re-scans find more channels, if it's randomly using invalid positions. Not sure why the twin reports 4 positions since it's only got two inputs.

EDIT: It looks like the inputs are not shared, I tried all of them one by one and as far as I can tell each input is linked to one of the two tuners, and the dish position is always AA. I'll try a scan with just one of them on AA only, see if that makes a difference.

EDIT 2: Using just position 1 (AA) of one of the tuner I got a few more channels, but still not Freeview. Most of the channels found aren't actually playable, it's finding things like "Discovery" unencrypted on 12382.5H which isn't right. Some like Sky News are playable fine, so the hardware definitely works. Could the dish be misaligned or the cable damaged and get only some muxes ?

I've read that the Freesat EPG is broadcasted from a different satellite than the Sky one here : https://forums.digitalspy.com/discussion/1646764/not-receving-all-freesat-stations

I hadn't realized that, since the dish was installed by Sky a few years ago could they have aligned it just right for their service but left out Freesat ?
Is that physically something they could have done ? Maybe I should call someone who doesn't work for Sky to align this again

All the services are broadcast from the same satellites, Astra 2E 2F and 2G. The only hardware issue I can think of is polarisation switching. Can you receive both H and V muxes, or are all the V ones missing?

No I'm getting a few H and a few V, that's not it.

I did notice yesterday that the wall socket was very badly done, one of the cables had the shielding touch the copper. I re-did it myself this morning, there's always a chance I did an equally bad job of it but my multimeter says I have continuity between both cable's shielding (likely in the LNB ?), but both conductors inside are properly isolated so that should be good.

Scanning now I'm getting completely different channels. Still no Freesat, but not one in common with what I was getting yesterday somehow .. I called an installer from the area earlier and he told me the LNB they put on Sky+ dishes would not work for Freesat, and he can sell me one that would for 20 euros. Worth a try I suppose, for that price I might as well try changing it and see if that helps.

So I changed the LNB for an universal one and it doesn't seem better.
Although the new LNB doesn't really fit in the arm so it's not locked, it might not be very stable, I do get ITV quite well with it, just not Freesat. I'll see if I can find an arm that fits the new LNB.

Alright, changed the LNB for an universal LNB and mounted it properly, and I can only get ITV.
I'll just get someone to come and re-align the dish, that's the only thing left to try out I guess

Nope, actually it's a tvheadend issue now. Before I changed the LNB, VLC couldn't pick anything up but I just tried it again and with the new universal LNB I've got VLC picking BBC One on the first try. Interesting ! Something is off in tvheadend, I wonder what it could be, I feel like I've messed with every setting at this point.

Figured it out, it was of course the only setting I had not touched. I enabled 'FE Supported' in the source settings and it all started working, I can now see the Freesat channels.
I do think I needed to switch to an universal LNB too, since before that vlc wouldn't work either, but that was not my only issue.
I'll test it some more but I think I'm finally good !

Im in the same boat now. Decided to get rid of Sky Q with a Wideband LNB and had a Digibit Twin already but that does not detect the Freesat channels. Got my hopes up when you mentioned the FE setting but that box is already checked in my settings so must mean the Wideband LNB is not compatible with the Digibit Twin?

Correct, I had to get a regular universal LNB for 20 euros in the local sat shop. It's easy to change yourself if you can access the dish.

I later installed a second dish to get French channels, using DiSeQ switches, works like a charm on the digibit twin !