This is the Firefox extension I use, I would check the headers your browser passes with WhoAmI to verify your user-agent, alternatively you can use invidious to get around YouTube’s bullshit.

I host a public Invidious instance for folks with a Canadian IP - https://inv.halstead.host/

I have to use Chrome to access a couple of sites that don’t play nice with Firefox.

I bet those sites will play nice if you switch your user-agent to display as chrome.