Thanks for the reply, but I've already been getting dovecot from Homebrew for many years now, with a local formula tweak to compile in MySQL support for auth tables.
I'm exploring the possibly of switching to building from source, to partially or totally decouple dovecot from semi-automatic Homebrew upgrades that often lead to breakage.
In particular, breakage often occurs when I upgrade MacOS, which triggers a flurry of more-or-less mandatory Homebrew package upgrades, which may break dovecot (or MySQL underneath).
I've also been considering containerizing dovecot, and running either under Docker or perhaps in the cloud, but that requires running within a Linux image (not actually a problem, but has a different set of configs from what I'm now using under MacOS), and it requires an approach for mailbox storage that interacts well with backups (e.g., that efficiently backs up small deltas for modest Maildir changes, rather than backing up an entire Linux container or even the entire Maildir directory structure each time).