I am using the official stable Andriod 8.0. the picture in picture mode which works fine with pixel devices having 8.0 on apps like YouTube, chrome etc is not working in any of the nokia 6 device my friends or family has. Do i need to change some settings or is it a software issue? I
Picture-in-Picture won't work with YouTube unless you've got YouTube Red, which requires a subscription and is only available in a handful of countries.
On my phone PiP works in VLC video player. Can you download the app, play a video and press Home to see if it work? I believe Google Duo supports PiP too.
There are quite a few topics related to PiP on this forum and most of them are people complaining because they didn't know YouTube's PiP is a premium feature.