One of the first crypto personalities in Norway did this back in 2011. Even had an article in the local paper. “Local man heats bathroom with his computer”. Basically he had water based heating in the floor on his bathroom and had hooked the water cooling on his computer to that. Even had a script that would “start doing heavy calculations” when the temperature sunk below a threshold.
I was kinda considering this to use up the excess production from our solar panels, because the net metering is only returning a fraction of the market price. It will depend on the ROI from a small homelab-sized mining rig.
Even with the increase in prices, electric heating is still much more expensive than gas heating (unless you use a heat pump, but then you're not mining anything).
