I can use Teams on the stable version without any issues. You might have cross-origin cookies disabled, which will stop Teams from working. PS. FF:v110.0.1 (64-bit), macOS: 13.2.1.
Oops, sorry. I was using the Office 365 Teams (teams.microsoft.com), which runs ok on FF. I can confirm the Teams for the personal account (https://teams.live.com/_#/unsupportedBrowser) is not supported in FF.
Those cookies are disabled by default in Firefox. Are you saying that to successfully use Teams one has to alter their browser configuration to make it _less secure_?