In which country are you seeing that?

For me the biggest offender are usually Google products and sometimes the lazy-coded website written by incompetents and whose audience is the tech illiterate (i.e. some websites involving schools/teaching) that just tell you "use latest Chrome just to be sure, download here" to, well, just be sure. Notable mentions for government websites that are like 10 years in the past and that are still on the "Supports Firefox" side because, well, they are just always late to everything.

I live in Australia and I can't log into government services using my myGov account on Firefox. Works fine on Chromium.

Usually that's because of third party cookies the government websites love to use for authentication. FF and Safari by default blocks them but both can be disabled temporarily to use those websites. Chrome is more lax on them since ad networks love cross origin cookies as well.

I have no issues with mygov in firefox (on linux of all platforms). I don't even whitelist ublock origin on that domain. Check your other extensions.

MyGov works fine on Firefox but I do use incognito window with no extensions for them. I’d say it’s probably one of your extensions.

I live in Australia and have been using Firefox for all my myGov needs without even thinking about it

Which service do you have issues with?

Just to test I just logged into myGov then through Firefox and it worked fine.

Wow. Force-Supporting the same company they're battling daily, on multiple issues.

Lack of joined up thinking.

While governments battle big tech on some issues, they are very much on the same side on others. They both want more tracking for example - the governments want to regulate it, and there is a battle for control of the data, but both want the data to be collected by someone.

Seems really dumb to let a crappy bank site dictate what browser you use for everything else.