Best guess is standard MS buggery.
I had teams running on my phone, but removed it on account trying to improve my mental health. The other day I needed to use teams on the go, and I tried using firefox on android. No dice, browser not supported, why don't you try our client? So I tried desktop mode, found out that I still had chrome installed, then tried opera and at last I even installed edge, and tried all in desktop mode as well.
I get that some functions may not work in rando mobile browsers, but teams noped out of every try. So guess who still isn't accessible on teams.