No issue for me, sounds like you’ve got some settings they don’t like, rather than explicitly blocking Firefox.
However I’ve had worse websites that just simply don’t work in Firefox at all. I mean, they do load, but there’s no ability to scroll, thus you cannot see the bulk of the content. An example: https://idno.vattenfall.co.uk/
No issue for me, sounds like you’ve got some settings they don’t like, rather than explicitly blocking Firefox.
However I’ve had worse websites that just simply don’t work in Firefox at all. I mean, they do load, but there’s no ability to scroll, thus you cannot see the bulk of the content. An example: https://idno.vattenfall.co.uk/