I've had this issue, I found it was related to my NIC and after a few minutes of downloading anything my network (on the computer, software side) would crash
I have an old ISP provided router and my wifi card is an Intel AX210 iirc.. Disabling AX on the router side (and forcing it to AC) is what fixed it for me.
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.
Have you tried limiting the download speed?
I just tried various limits, and still having the same issue
I have a 500Mbps symmetrical fiber connection
Are you using your ISP's modem/router?
Try a bufferbloat test: https://www.waveform.com/tools/bufferbloat
If this is the cause, essentially the ISP is buffering a lot of data on their side to make sure it's ready to send to your router ASAP, but that also means that anything else being requested gets queued behind all of that Steam download data, so it takes forever for anything to load although it should eventually load.
You can also try pinging google or something while downloading, you might see the ping response times go from a few ms to seconds.
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