I have the exact same issue when using my tablet. The latest version available for manual download for Synology diskstation 7.2 is PlexMediaServer-1.41.6 which yields the error “This package requires DSM 7.2-70000 or older”.
Hopefully a version be released soon to sync with the Android app requirements.
@tom80H the community version for DSM 7.2.2 is 1.40.4 - manual install version available is 1.41.6
The manual install version for Plex cannot be installed due to the above error (requires an older version of DSM) and the community version 1.40 yields the out of date error, so we have a catch 22 here!
The NAS compatibility list is a good source to confirm the architecture of a NAS model. I’ve been searching on Syno’s homepage myself yesterday and couldn’t find any reference to ARMv7 vs. ARMv8 (it’s not even mentioning that the Realtek RTDxxxx chip is an ARM chip).