There were two WebRTC fixes put in since the last release... Basilisk-Dev committed a fix to a general build breakage, and I committed a fix for building on Mac ARM... I haven't tested with Basilisk/Silver but it should work now I think.
https://repo.palemoon.org/MoonchildProdu...ssues/1982
https://repo.palemoon.org/MoonchildProdu...d869ede81b
https://repo.palemoon.org/MoonchildProdu...ssues/1982
https://repo.palemoon.org/MoonchildProdu...d869ede81b