I have a sony 43xd8305 on the latest firmware and have found that my Prime Video app is now capping content that previously played at 4k HDR to 1080p SDR, is this a known issue, or is there a fault in my system somewhere? according to all i can find online sony tvs from 2015 on should play prime video at 4k, assuming connection is fast enough?
4K videos on Prime are usually separate and have a UHD banner in the corner of the thumbnail. Are you not seeing those anymore?