I recently bought a UZ801 USB Wifi 4G dongle for 10€ incl shipping from China and flashed linux onto it. It's a full-on router running OpenWRT in my workshop now. Can definitely recommend tinkering with such boards, I'm having a lot of fun, especially because of the limitations (384MB RAM, 2GB flash). A lot of tools I wanted on there I had to reimplement in Rust to be more resource-efficient.