I had this issue and there’s an easy fix - there’s a bug with GMaps street view where it starts to lag on FF on Linux specifically, but as soon as you spoof your user agent to something Windows based like FF Windows or Chrome Windows, it’s back to full speed. So get an extension to change your user agent string to Windows and you’ll be fine.

https://addons.mozilla.org/en-US/firefox/addon/uaswitcher/