Set up a new computer with MacOS 27 and joined it to Active Directory. Signed in with an AD account. The local home folder is created for the user but the users "Application Support" folder is set with ROOT as owner and the user (nor any application run by the user) cannot write to the folder. Various programs that require write access to the user's Application Support folder crash or fail. If the user manually takes ownership of the user's Application Support folder write access is restored and programs stop crashing.
I have never seen this with any prior version of MacOS. I have repeatedly erased AD user accounts and signed back in as the AD account and the same owner of ROOT is assigned the user's Application Support folder.
Just to clarify, this is not a problem with the OS Application Support folder but the user's Application Support folder.