Hi tom80H…
I found one thing the original plex file create for Synology spk name is
“PlexMediaServer-1.22.0.4163-d8c4875dd-x86_64.spk” (On March 2021).
at 27 March 2021 the file name has been change PlexMediaServer-1.22.1.4228-724c56e62-x86_64_DSM6.spk
Which i tested with older version plex server 1.22.0.4163 has no issue.