Given that the original ROM is no longer available, I'm trying to determine whether there is still a practical recovery path.
It's not impossible but serious experimentation needs physical and software tools and a deeper level of technical ability than most users have or will easily learn. It's typically rather time-consuming and bit of a hard slog, so even when the user is enthusiastic to have a go; most of the staff (self included) have learned to avoid such quests.
ConnMan keys stores network profiles against the MAC address of the WiFi card so check the MAC is persistent. Some cheap USB dongles have none programmed so the kernel assigns a random address on each boot; resulting in the new MAC not matching against existing stored profiles and requiring you to enter details again.
In the case of an RPi5 board it's more likely that the connection is bad as the onboard WiFi isn't great.
Use LE13 ..
Firmware can be added to https://github.com/LibreELEC/dvb-firmware or manually added to /storage/.config/firmware which is overlaid onto /usr/lib/firmware on boot.
For drivers; someone should just "grow a pair" and have a go at upstreaming the driver bits required. It might some learning and a few iterations to get things into an upstream acceptable condition, but until someone does that (and sadly it looks like it will never be TBS themselves) you're all stuck in downstream purgatory.
And here it is
I'm still not a huge fan of flatpak, but it seems to work and others are keen to own all the maintenance. In the mid-term it clears the path to exorcising Xorg from the codebase which is a bigger win. Ho hum 
Kodi Piers (22) now contains some major changes to how Kodi handles GUI/video output on Linux. Most changes are addressing functional and feature gaps in GLES/GL rendering support. However they also cleanup older VAAPI code and fix bugs. I guarantee there are also more bugs to be found and hopefully fixed.
In short: Kodi has changed. Users with configurations that previously relied on fallbacks/quirks/bugs may find their configuration needs to be adjusted as the dependent fallbacks/quirks/bugs have changed or no longer exist.
Using D2P (as you were) is wrong for an Intel GPU device, it should use EGL. It's unclear if you were also trying to use DRMPRIME paths but that would also be wrong. Your old config was dependent on a load of fallbacks and quirks. Kodi settings needs tweaking to force EGL output and hide the wrong settings when using VAAPI .. it's on a to-do list.
If you configure Kodi for 4K desktop with only 4K whitelist entries Kodi will upscale everything to 4K. If you configure Kodi for 1080p desktop and provide 4K and 1080p whitelist entries Kodi will scale anything under 1080p to 1080p and will render 4K at the native media resolution; this is generally considered "best practice" as Kodi is not modifying the original media (1080p and up) and most TV's are better at scaling 1080p to 4K than Kodi. Running a 1080p desktop normally means the GUI looks sharper and the HTPC device uses less CPU/IO resources resulting in smoother navigation.
In summary: something in the Alpha state development release you are using has changed. You have been advised of a different and better configuration to use. You have confirmed that different and better configuration works. However you are unhappy at having a different configuration.
"You can please some of the people some of the time, not all the people all the time"
AFAIK nothing changed in aeons so take the current RPi2(3) image and write to eMMC, then set the dtb and slice overlays. There are probably some other upgrade threads in the forum if you search around.
Cross refencing .. because opening the same ticket to the same people in two locations always wins friends
I don't see a "throttled" warning at your log, so I don't think it's a PSU issue.
The "throttled" message would be a thermal issue not a PSU issue. You're thinking of "undervolt" perhaps.
If you move the dongle/remote combo between RPi4/NUC systems does the problem follow the move? .. i.e. is it a specific dongle having the problem or all of them?
On the current system; with one of the USB drives moved you can move the dongle from USB2 to USB3 ports. Any change?
If you have two drives powered from the board my hunch would be that when the board is booting and everything is in an active state the drives can pull enough power to result in the remote USB dongle not receiving enough to power on. This is probably a borderline case so it might still work occasionally. If you then remove/reconnect some time after boot the board is now in a less active and more power-stable state so the remote USB dongle reliably works.
If the hunch is in the correct direction, perhaps using a higher rated PSU might work, e.g. the 5V/5A spec for an RPi5. Or connecting the drives to a powered USB hub, or if one of the drives has as USB 'Y' lead (to draw power from multiple USB ports) connect the non-data plug to an external USB phone charger to reduce power draw from the 4B board.
Double-check that you are using a current nightly. The latest LE13 images are at the bottom of the page not the top; older images will probably use a repo version that no longer exists on the server.
If that's not the issue, you need to investigate whatever local-to-your-install networking problem prevents the RPi5 from connecting to the repo (which is live/accessible). If you are using WiFi ensure "wait for network" is enabled with a long enough delay.
(re)boot, leave the OS a couple of mins, then replug the device, SSH in and run pastekodi and share the URL.
No idea what the issue is (and you haven't provided debug logs to help the guessing) but LE12.2 is a dead codebase so bump to a current LE13 nightly and move forwards from there.
how can I find that out ?
If the panel advertises 4K modes it has 4K (or more) pixels. If you send it a 1080p signal the internal processor upscales 1080p to the native 4K panel resolution. It does that better than Kodi (and with zero load on the HTPC). Or you have a magic screen that somehow changes its pixel count when you send it a 1080p signal
Sat-TV isn't upscaled to 4K (only to 1920x1080) !
Yup, Kodi upscales to 1080p and the TV upscales 1080p to the native 4K panel resolution. The TV will show that it has a 1080p signal but there are always physically 4K pixels in the screen, no?
The TV panel is 4K native resolution so the TV has a ton of advanced scaling capabilties. Kodi can also upscale, but they are not as advanced as the TV's ones. So run the GUI at 1080p, allow Kodi to upscale SD media to 1080p, but allow the TV to handle upscaling of 1080p to 4K as it will do a better job.
Then play some media and pastebin another debug log.
