Here are a few other responses from community influencers:
This sounds like a scenario where you are hosting an application/service for end customers, e.g. a SaaS offering, but as rich client where RDP protocol is required.
The solution is to enable Remote Desktop Services to allow multiple users working simultaneous on a VM.
You could either build a RDS farm in Azure yourself, or you use Windows Virtual Desktop as Gateway/broker Service to publish the application, which I would recommend.
You need to use WVD with Windows Server-based session hosts though, not WVD with Windows 10 Multi-Session - this is because of licensing reasons.
Since you are providing a hosted service, the access of the end customers would need to be licensed via RDS Subscriber Access Licenses (RDS SALs) obtained via SPLA, for hosted scenarios like this there is no other option then to use SPLA licenses because usage of RDS role is not covered with the Windows VM license that Azure offers.
Does not change that you need RDS and the licenses (RDS CALs - or RDS SALS via SPLA when it is about a hosted solution like described by the OP).
Since this thread was revived via the new post, and since there were changes, some additional information: You can now also offer Windows Client OS (Windows 10/11 Multisession) in Azure Virtual Desktop as basis for your hosted, custom services/apps, not only Windows Server how I described.