I definitely believe people underestimate the potential of OpenWRT as an app platform. Before getting sidelined with work I did some proof of concept WebRTC SFU on it https://github.com/atomirex/umbrella which worked surprisingly well.

Was also surprised, then not surprised, to learn it's used as the front end on many of the new generation of 3D printers.

I have a bunch of old WD MyBook Live NAS drives (PowerPC CPU) from an older project, and was surprised that OpenWRT was the best way to get a modern linux on them:

https://openwrt.org/toh/western_digital/mybooklive

They're slow, but great for stuff that doesn't need to be fast.