I just opened up Google Earth in Firefox to see what would happen. It's buttery smooth with basically zero lag on loading assets, and zero lag zooming and dragging around on my 240Hz display.
I have a 1gbps symmetric fiber connection and I'm running NixOS. my Firefox Nix Home Manager config is here:
That's a non-commercial license. It's not open-source, just source-available.
https://github.com/vb000/LookOnceToHear/blob/main/LICENSE