Andrew, with the additional patch "0002-Add-combined-hevc-alpha-decoding-patch.patch", I no longer had the crash I had previously reported.  Since both you and Andrea successfully tested, I would like to checkin ffmpeg-8.1.patch11, ...patch12, and ...patch14 as long as you concur.  But why 13 skipped?  Checkin would include patches:

0001-Add-two-patches-for-decoding-hevc-alpha.patch

0002-Add-combined-hevc-alpha-decoding-patch.patch

0002-Add-simple-hevc-alpha-encode-profile-with-hvc1-tag.patch

0003-Fix-h265_alpha-profile.patch