Plex does want to get this working again on the x86_64 devices. As mentioned, there is a technical issue right now getting the app working properly on these devices, it’s not just a bug that can be fixed with changing some code.
To be clear, the issue started with a specific version of the app, I’d need to check exactly the version but it was somewhere around 8.13. If you install an earlier version of the app, that should get Sync working again. Android (mobile) beta release notes - #399 by romancamelia
For that linked thread, I’m not familair with that issue but it’s possibly related.
