As @mark.clegg already pointed out: Unfortunately, based on the way linked library versions work, whenever one of the packages that this one is build against gets updated, you'll also have to rebuild mythtv.
In this case, x265 got updated to a new version over the weekend. The maintainer of ffmpeg in extra was notified of this and put out a rebuild version of ffmpeg alongside it. For the AUR, it does not work like this. Here, you are your own maintainer and have the rebuild your packages yourself, whenever their dependencies get updated and the linked libraries break as a consequence.
Pinned Comments
JohnLBergqvist commented on 2023-04-10 15:56 (UTC) (edited on 2023-04-10 15:57 (UTC) by JohnLBergqvist)
This package replaces the previous 'mythtv' AUR package. It has been renamed to comply with Arch's VCS package guidelines.
I hope to update the various mythplugins AUR packages soon