Real advice - if you want stable HDR without crutches, it's easier to put Windows 11 Pro Retail, it is activated by the same licence, and multimedia stack there is up-to-date and updated. LTSC is good for servers and offices, but for HTPC and HDR-video with MKV it is a real pain.
Yes, I'm coming to that conclusion. I've been busy so not had much chance to play, but I still can't get any further with 11 LTSC. I'm going to have to bite the bullet and install retail... for the first time in a long time, lol. Either that or spend even more money on a Ugoos AM6B Plus which seems to be the current best thing to get. The mini PC was bought for this purpose but for the previous non-HDR TV. I'll try Windows 11 retail first though.