My desktop Raspberry Pi 4 used a USB HDD disk. Old fashioned spinning platters. It was 4TB and much cheaper than SSDs. Turns out this was probably a mistake. Even with a nice metal heatsink case the Pi was always hot to the touch. I recall about 140F. I sprung for a new 1 TB Samsung USB SSD and (after the usual hassles) got it all set up yesterday. The Pi was noticeably cooler, just over 100F. I suspect the power drawn by the USB HDD drive was enough to heat things up, but probably not enough to cause failures.

Now I wonder if some of the early problems I had getting things like WiFi and Bluetooth to work were heat / power related. Anyway, now I have a proper backup drive (the old HDD). Will be able to organize my files now (really :^)