Or is this a bad idea?
Reading through !selfhosted, I think I have found a new hobby. I have an old laptop HP ProBook 450 G5 4WU81ES.
16gb ram, solid CPU, shitty integrated gpu, and only 256gb ssd. Barely enough for system and some apps. Battery life maybe 30min unplugged so I take it as an UPS.
So the question again is, can I have permanently plugged external hdd to use as extension for this purpose?
There are certainly better ways to do it, but lots of people use external disks. I would put anything that needs speed on the SSD (so like a database or whatever) and anything else (media, isos, etc) on the external drive. It’s probably also worth thinking about a backup strategy, at least for anything there that matters.