Update: I went to the ATT store, brought the PepWave with me, and about 30 minutes later walked out with a new 5G ATT SIM card on their prepaid $35/month for 15GB plan. They did have a cheaper unlisted plan, but it was $30 for 5GB which seemed like a bad deal.
Question: why is the IMEI not printed on the PepWave itself? I had to call home and have someone take a picture of the box for me.
Initially, it didn’t work, but after futzing with the APN, I got connected: AT&t SIM issues with 5G - #46 by soylentgreen