> on my Windows 10 box, a Steam update can take half an hour or more
This hasn't been my experience at all. On my Windows 10 box with an aging third gen i5, a 50Mbps connection, and an SSD, Steam client updates rarely take more than a minute or two.
Mine is an AMD <mumblenumbers> with a 1Gbps connection and no SSD. But when Windows 10 comes back after an update, the machine will be unusable for at least an hour whilst it does <something>. Steam updates take forever. Installing Postgres the other day took about half an hour, of which at least 20 minutes was installing VC++ redistributables.
The problem with Windows 10 seems to be that it's wildly inconsistent and susceptible to the tiniest variations.
Just get a humble monthly subscription. For $12 a month you will never have to worry about not having enough games even if you only play on linux.