Linux users unable to see my shared screen (Windows Zoom app) when joined by Firefox

Hi, I have some colleagues who cannot see some Zoom screen sharing when they join meetings. Can anyone help me identify the issue/settings that would allow them to join as they typically do.

Here are the technical details I can provide:

• Users (2) Details
  • Linux OS (not sure what flavors/version)
  • Zoom by Firefox: Issue
  • Zoom by Chrome/Chromium: OK
  • One user advised that the Linux Zoom app didn't work for him; I didn't ask for details.
  • Both users have some issues trying to share, but have sufficient workarounds.
• My Details
  • IBM ThinkPad X1 with MS Windows 10 Pro
  • Zoom Version: 5.12.8 (10232)
  • Meeting Settings: I've enabled most of the bells and whistles available to me. I allow my invitees to join before me and start sharing while others are sharing.
• My Boss's Details
  • Mac OS
  • Zoom App (I think)
  • Meeting Settings: Uses the company default (fewer bells and whistles). Host must admit invitees. Only host can start sharing while others are sharing.
• Circumstances
  • In a meeting created/run by my boss, both users can see his screen when he shares.
  • In a meeting created/run by me, both users can see my screen when I share if they joined the meeting with Chrome/Chromium.
  • In a meeting created/run by me, neither user can see my screen when I share if they joined the meeting with Firefox.