changing [mysqld] - init-connect = 'SET NAMES utf8mb4' + skip-character-set-client-handshake collation-server = utf8mb4_unicode_ci character-set-server = utf8mb4 does successfully workaround the problem; 'mysql_fix_privilege_tables', and the rest of the update succeeds, ... Phase 4/7: Running 'mysql_fix_privilege_tables' Phase 5/7: Fixing table and database names Phase 6/7: Checking and upgrading tables Processing databases information_schema performance_schema test Phase 7/7: Running 'FLUSH PRIVILEGES' OK notably, immediately changing it BACK [mysqld] + init-connect = 'SET NAMES utf8mb4' - skip-character-set-client-handshake collation-server = utf8mb4_unicode_ci character-set-server = utf8mb4 and exec'ing mysql_upgrade --force STILL, now works, ... Phase 4/7: Running 'mysql_fix_privilege_tables' Phase 5/7: Fixing table and database names Phase 6/7: Checking and upgrading tables Processing databases information_schema performance_schema test Phase 7/7: Running 'FLUSH PRIVILEGES' OK not sure what that tells me -- whether this is a one-time-fix issue, or that the subsequent '--force' is simply not ATM sensitive to the problem, this time