Roku, who has about 50% of the streaming device market in the US, supports entering passwords via their mobile apps.
Having to enter a password on a streaming device is rare event for me at least. Almost all of the apps on my Roku support using an off device web browser to authenticate.
I don't believe that was an option when I set mine up but that was a few years ago. Also there is a wide range of Roku devices and TVs with differing capabilities so even ig mine didn't it might be that some do support this. I honestly don't know.
Having to enter a password on a streaming device is rare event for me at least. Almost all of the apps on my Roku support using an off device web browser to authenticate.