There’s lots of uses for it.

An overlay network like nebula uses “lighthouse” nodes as ways to reverse proxy to all the other hosts in the overlay. I’ve used og eeepcs as nebula lighthouses before.

“Dumb” 3d printers honestly don’t need much to bring their feature set in line with expensive ones. I still use an old netbook to control two. The screen and keyboard are great when I want to check files. Slicers and whatnot can easily run in low resource settings on those computers.

Vents allowing (and many netbooks do!), you can slide the computer into a shelf and use ssh to perform tasks on it. There’s a bunch of stuff that an always on computer with a built in battery backup can be used for at times, especially if it’s on a wired connection and you can use the wireless interface.

People will say you should be afraid of the batteries exploding or venting. I’m honestly not too concerned, but be sure to check them maybe once or twice a year.