Admittedly we have not tested on firefox as much, but I suspect that is happening is that we have a race condition in waiting for the 30+MB package of wasm and data files to load.
This is impressive and shows a lot of dedication!
How are you hosting the site and assets?
Hetzner, with Cloudflare to do the CDN for such large game assets.
I generally think it'd be wise to develop for either Safari or Firefox first. Then fix for Chrome after.
i.e. develop for the underdog(s) first.
same issue in FF I think. "Couldn't start server"... and it is a pretty quick timeout, like 2 seconds
The link with the Curse of Monkey Island works fine on my Firefox mobile