I joined Plusnet after leaving Talktalk in May of 2020. Straight away I noticed that Youtube was running quite poorly but didn't think anything of it because I read that companies were limiting bandwidth due to the global situation and more people being at home. I just put it down to this.
However, this has lasted all year and is still the case right now. I have Google Wifi and a couple of months ago I changed them over to Deco M5 Wifi, but the problem still existed. I have tried plugging the phone line straight into the router, then straight into all my devices but the problem is still there.
I have the same issue on Youtube on my Sky Q box, PC, Xbox and PS5. All these devices are hard wired with ethernet and not using Wifi.
I saw that someone tried using a VPN and connected to YouTube and it worked, and sure enough I just done this on my PC and all videos load straight away, no buffering, no pre-downloading it just works. Even the 4k streams don't buffer. I turned the VPN off and loaded other videos up and I get 10 seconds of video, then 2 mins of buffering. 720p streams even struggle.
I never ever had this issue with Talktalk and I must admit I am kind of regretting leaving them for Plusnet now...