If you have to reclaim / expense it a cheap USB-C Ethernet adapter is a next day thing from Amazon. Will prove or disprove if it’s the dock.
Still think you should try connecting direct to the Frtizbox with no powerline adapters in the link…as a systematic approach 😉
After configuring a wifi connection I spent an hour on a Teams call with Support earlier and my screen share didn't have any problems at all so it *might* be fixed. I'll be doing some more testing next week.
I'll connect one of my old PCs laptops direct to the router over the weekend too but this won't have Teams installed so won't be able to test much on it.
Also, I wasn't sure about some of the statistics from the bufferbloat test - there's more latency on the upload (which is higher than the download) and I think this might skew the figures.