Microsoft did release MSI packages for older systems to update the RDP client to version 8.1.
msiexec /i "RemoteDesktop.msi" /qn
If you are using Active Directory:
The Microsoft Remote Desktop (MSI) download—formally known as the Remote Desktop client for Windows—is a legacy standalone installer designed for connecting to Azure Virtual Desktop, Windows 365, and Remote Desktop Services. microsoft remote desktop msi download
Use the Remote Desktop client to connect to Azure Virtual Desktop Microsoft did release MSI packages for older systems