Spawning ffmpeg for stream transcode and using m3u playlist to access the channels in my mobile devices.
Does Tvheadend have a way to transcode a recording from MPEG2 to H264 on disk (not on-demand via a stream profile)? I think that's the one thing it was missing for me when I looked at it a 4 or 5 years ago. I think it was hacky like MythTV's transcode, except the transcode solution I have in MythTV also broke commercial skipping.
These frontend crashes have not adversely impacted the ability of the backend to record
My issues are MythTV backend crashes, when switching recordings and accessing the built-in web UI via :6544. Single process multi-threading isn't all that great when you have bugs. 
Still dont understand why anyone would want to try something else that is not user friendly, may not work, cause crashes, or whatever.
Today, I am not sure I would recommend it which is why I laid out the problems I have seen with MythTV. But you must realize that MythTV is ancient, it has been around at least 20 years already, so Tvheadend wasn't really an option back then.
Tvheadend isn't so easy either, in my book. The UI is slick, when I gave 4.0 or 4.2 a ride, it was a little difficult to get it running, and a bit annoying that there was no SQL database backing it (just JSON files). But it is far more modern than MythTV, if I recall it uses a microservices architecture, so that's pretty nifty.
tbh no idea, never got it working and the website itself is not helpful either
but if someone tries I am happy to hear feedback
from the outside it looks like vdr just more complex and even less user friendly
MythTV does work, and you nailed it pretty much on the head tho. It's way more complex than it needs to be and not very user friendly. There is a setup GUI which only runs under X, it's awful. Most of the crap you want to get done you better know SQL, because there is a lot of backend DB tweaks -- just to avoid the UI to some extent. It is also, at least for me, a bit buggy and crashes occasionally when switching recordings while watching LliveTV. They have a more or less unsupported web front-end called Mythweb, which they push you to the built in one in MythTV backend that crashes the backend when you use it, so much for process isolation.
One thing noteworthy is PVR IPTV Simple & MythTV PVR in Kodi will crash Matrix 19 on start up, never ran them together before, but the Pluto add-on had PVR IPTV Simple as a dependency, so I ended up just uninstalling Pluto and PVR IPTV Simple and moved on with my life. Didn't really need it. But there are historically, at least for me, problems with MythTV PVR addon or PVR in Kodi in general, deadlocks and the sort that still occur.
Perhaps posting a debug log of the failure scenario would be useful. Assuming the parser is checking closing tags then probably omitting the closing tag causes the XML file to be ignored completely.
I have been using advancedsettings.xml with a shared MySQL DB for probably 8 or 10 years since XBMC 13.0 on multiple platforms, early on I used Windows, but now I am on Amlogic & RPi4 devices.
Path is /storage/.kodi/userdata/advancedsettings.xml
Not sure if what you have above is a typo, but there is a slash between .kodi & userdata, and the file is named "advancedsettings.xml" not advancesettings.xml
Gave the latest box nightly a shot on a Vero 4K+ (S905D), pretty impressive progress. Only thing noticeable was the seeking issue, and some sort of brightness flickering. But it seemed to use hardware decoding, and CPU usage is usually in the ballpark for this device. I am pretty basic user, tho, 1080p, regular old HDMI audio, mostly x264 encodings. Much like my RPi4 setup on LibreELEC 10.
