I was written about
mpv https://mpv.srsfckn.biz/ is well player for HLG and this is so as minimum for last version (and with hardware acceleration in my case with
--hwdec=auto in mpv.conf):
so problem with watching HLG records is solved but for live watching (and play records in my favorite KMPlayer) some HLG->SDR shader with quality not lower than
mpv is still appreciated.