This is their choice not to configure it correctly. You can set up Azure RDP and use Remmina as a front end to FreeRDP or just FreeRDP by itself.
Also why are they using a browser “client”? That is also an odd configuration. You don’t need a special client. I use Firefox on Linux (with a container - love those) to connect to the Azure Desktops.
I do all my windows work from a Linux machine. Recently I traveled to another country and did all my clients Windows (Azure remote desktops) work from a Steam Deck (Arch linux), lol.