@YasuTiger Apologies for the delay in response and all the inconvenience caused because of the issue.
Surface pro X is ARM based, Surface pro 7 is x86 based so should work the same as the other devices you mentioned. For the Surface pro x did you use the arm version of the client? https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/clients/windowsdesktop#install-the-client and did the web version work properly?
Thanks