I did the following:

1) Picked up a new (shrinkwrapped) Verizon 4G LTE SIM card from Droidstop

2) Suspended my Pixel 1 (link)

3) Installed the SIM card

4) Resumed the Chromebook

5) Tray -> Network -> Activate cellular

6) It initially displayed a Verizon registration page, but then showed an error message that the SIM card is not compatible with the device

7) I closed the dialog

8) Repeated steps #5-7 a couple of times, to no avail

9) I noticed that I could disable wifi and access internet sites (ipchicken) over LTE for a couple of seconds before it shut itself off

10) Suspended/resumed the Chromebook once

11) Now LTE works fine; it doesn't prompt me to activate it anymore

This is better luck than I had with the original T-Mobile SIM card that Droidstop gave me, which had no connectivity at all.