VMware esxi 7, win10 sandbox. Debian hosts for docker. I also run some a couple of i7 Mac mini's. I try to host on a balance of cheap, power efficient devices that I have spares of in case they blow up because I hate dealing with hardware compatibility issues. Since I decided this and shelved spares I haven't had any failure's.

Does anyone NOT use old equipment for a homelab?

I've got 4 x Dell R620 servers, though I've recently shut down 2 of them because they are running in an unconditioned garage closet and it's been absolutely hot this summer.

Also have 4 old 16-disk trays from a Nimble SAN, but again only running one of them (16 x 3TB SAS) for heat reasons.

I also have the Nimble controller but the firmware is borked and I can't get a copy without a service contract and you can't get a service contract on this old hardware. I briefly had it working running Linux on the two controllers, which works but is a bit tricky since shutting down one side causes the other side to shut down unexpectedly. So I'm leaving it unused until I can either sell it or find a copy of the proper firmware.