1080p/h264 and 4K/h265/hevc should not be a problem. 4K/h264 can be a problem.
Not sure what you mean with AFR. Automatic Frame Rate? Yes.
Add-ons, sure. IPTV, not really my field of expertise.
HDR development is still ongoing, the first steps have been made.
For the latest details, read https://libreelec.tv/2021/11/03/libreelec-matrix-10-0-1/
yeah, just found that release notes.
borrowed a rpi4 from a friend, hopefully will test this all today or tomorrow.
best scenario is to get the release or a nightly build?