If I am reading the correct information because of Hardware restraints No H.265 support for all the Rasberry Pi’s except for Pi-4 with software.
So pretty much all my Pi’s are outdated 
Raspberry Pi 4 supports HEVC decode in hardware on all OSMC releases.
Pi 2/3 is software only on recent versions of Kodi, but pre 18.9, you’ll get some HEVC hardware acceleration via QPUs.
So the latest OSMC on Raspberry Pi-3 for Kodi will work H.265 ? Without doing anything ?
No – as explained above, it will not work on the latest version.
Sorry read it backwards , so earlier versions 18.8 and back work. Bummer since H.265 is a god sent for less drive space.
AV-1 will be too.
On the older RPi hardware with the Kodi 18 releases there was some hardware support but this basically enabled smaller less complex encodes and IMO isn’t something that someone should downgrade for since you can’t just throw any old file at it and expect it to work. The RPi 4 seems to handle most any non-HDR files just fine (unless your a fan of the tone-mapped look). If you want HDR support the Vero has support to play that.