Step 0: Plug in your USB 4G-LTE Modem (TPE-USB4GLTE)
Step 1: Run ifconfig and find your device (under OpenBSD 6.6 it shows up as umb0)
Step 2: If there is no pin set run the command below to set an apn and bring up the modem (replace umb0 with the device name shown in ifconfig and att.mvno with your cellular provider apn)
ifconfig umb0 apn att.mvno up
Note: If there is a pin set then do this instead (replace XXXX with your pin and att.mvno with the apn for your cellular provider):
ifconfig umb0 apn att.mvno
ifconfig umb0 pin XXXX
ifconfig umb0 up
Step 3: Set a nameserver (if you have none set already the below will append one to your /etc/resolv.conf file)
echo nameserver 208.67.220.220 >> /etc/resolv.conf
Step 4: Test your connection
ping 64.20.171.171
Step 5: Test everything is setup correctly including DNS
ping thinkpenguin.com
After a few seconds hold down the ctrl key and while doing so tap the c key to cancel the ping request. If you see 0.0% packet loss or something relatively low and not 100% packet loss then you have successful setup your Mobile Broadband Internet connection under OpenBSD.