Hello,
The quickest and easiest method is to obtain a certificate from a public Certificate Authority (CA) and associate it with RD Web Access (when user access RemoteApps through RDWeb).
When connecting via VPN from outside the network, client computers typically trust certificates issued by well-known authorities by default. If a certificate isn't recognized as valid, it may reject the connection to mitigate potential security risks.
Once the public certificate is installed, it's already trusted by most operating systems and web browsers, eliminating the need for manual installation on each client's trusted root store, as required in the case of self-signed certificates.
Reference article:
Using certificates in Remote Desktop Services | Microsoft Learn
How to Create a Self-Signed Certificate on Windows | Windows OS Hub (woshub.com)Note: Since the websites are not hosted by Microsoft, the links may change without notice. Microsoft does not guarantee the accuracy of this information.
Regards,
Karlie