So, I slightly modified Windows version of thdmerge.
in theory it should prepare thd (trueHD) file for blu-ray muxing.
make file.thd and file.ac3 with ffmpeg
$ ffmpeg -i ~/vid_20210526.mp4 -vn -c:a ac3 b.ac3
$ ffmpeg -i ~/vid_20210526.mp4 -vn -c:a truehd -strict -2 a.thd
compile
gcc -o thdmerge thdmerge.cpp
run
./thdmerge a.thd b.ac3 full.thd+ac3
try to mux this resulting file with tsmuxer