The Raspberry is quite capable (has enough power) to watch online TV on it.
At the moment, Youtube is running smoothly in 1080p on my Rapsberry Pi 4 (4Gb. model). I'm pretty sure it would also run smoothly in 4K.
But if you want to watch Swisscom-TV / Netflix etc. I would recommend the OMSC operating system (OSMC -> Open Source Media Center -->
https://osmc.tv). Also, rather forward-looking, buy the 8Gb. Version of the Raspberry.
It will need some configuration, it is a developer platform. But it definitely won't take days... rather hours or even minutes.