Hi. I just want to share a story about the problem I had and how I solved it. 

I have 1 Gbps T-Mobile internet. Everything works well while my wife does not have meetings with her co-workers using Microsoft Teams. When she is having Teams video meetings with other 5-10 people, the internet on my laptop becomes very unstable and sometimes drops down to 0.5 Mbps for a few minutes (I measure using Speedtest). What is more interesting, for her, everything is working almost perfectly.

I have tried different solutions, but everything changed when I removed Zyxel router from T-Mobile and replaced it with my own Asus ZenWiFi XT8 (it's really powerful router). Today is the first day when the unstable internet problem is gone. It looks like Zyxel can't handle a bigger load. Like multiple video streams from Teams. When Zyxel is loaded more, internet instability appears.