Talking of cheap and powerful devices one can also look at Chinese UZ801 4G LTE (Qualcomm MSM8916) dongles. They cost like only $4-5 and pack quite impressive HW: 4GB eMMC, 512MB RAM, actual 4G modem sometimes with 2 sim switching support. Since it's actually old Android SOC there is even GPU and GPS in there. And a lot of work was already done on supporting them:
https://wiki.postmarketos.org/wiki/Zhihe_series_LTE_dongles_...
https://github.com/OpenStick/OpenStick
So yeah if you looking for hardware platform for weird homelab projects that's can be it.