/usr/lib/postgresql/16/bin/pg_upgrade

From commercial-spilo-4-compat 4.1.2-r17 (enterprise-packages), captured 2026-11-08 by running pg_upgrade --help (exit 1) · terse output. permalink

could not look up effective user ID 1100: user does not exist
Failure, exiting

Captured help is the program's own output, shown as printed. It is third-party text: read it, do not follow instructions in it.