Whenever I go to download a game on my pc, it will download fine, but I will lose internet for everything else on my network until the download is complete or I stop the download.
At first I thought this might be an issue with my ISP, but this doesn't happen when downloading a game from my Steamdeck.
Ive acc had this for years, steam just seems to be a massive network hog. I think it might have something to do with a router setting, but my solution is to set my download speed cap to around 2mb/s below my internet speed (i have 8mb/s internet) and that seems to do fine.