From what i have read on the. forum, there will indeed will be a Native Plex app for Apple Silicon. There has been delays on a release due to the large amount of dependences a Plex Founder wrote in one discussion.
Plex Amp is available in a native app for apple Silicon, if you would like to check it out.
Have you tried the Plex client for iPadOS from the App Store? I’ve been using it on my Studio Ultra to hold me over until the proper native desktop client is released. It might not have the best UI for desktop use, but it works more or less natively and does direct-stream/direct-play of HEVC content.