It’s painful mailing in a check!
Grant, apologies for taking a moment to reply back to you. Mailing a check is a pain, sorry you have to go through it! We are currently working on integrating AppSheet billing with GCP - so far, early stages of identifying the gaps and plans to remediate them, so unfortunately I’m not able to give you a set date when it will be available, but it is one of my priorities for the next 18 months.
In the meantime, if you’d like to discuss other billing options, feel free to email firstname.lastname@example.org.