Hi.
I have Greenpacket OA335M Cat.12 LTE outdoor modem which I'm willing to donate for OpenWRT development. It's working, however it has carrier branded FW for O2 Slovakia. I tested it with SIM card from other carrier and it failed to connect so it's useless for me.
This particular model supports LTE frequency bands B1/3/20/28A/42/43. So please check if any of those frequency bands are available in your location. Second hand market is flooded with devices like this, that's why this one ended in e-waste (and I saved it 
)
More details can be found in product specification.
Let me know if someone from dev team is interested into this.
bootloader is UBOOT 2015.10-rc2
Thanks!