My Steps:
stop all zabbix containers except postgres-server 15.x
export db with pg_dumpall (docker exec -it zabbix-docker-postgres-server-1 pg_dumpall -U username > upgrade_backup_15.sql)
Stop postgres-server 15.x
Edit docker-compose host’s postgres-server data directory to a new empty directory + set new version 16.x tag
Start only postgres-server 16.x container (using same zbx_env) (Creates fresh db)
Import db (cat upgrade_backup_15.sql | docker exec -i zabbix-docker-postgres-server-1 psql -d zabbix -U username) – No errors upon import
Start entire 7.0 stack – On first run I saw additional DB upgrade progress + successful