hello @NameHasBeenTaken welcome to the community 
As the name already implies there whole idea of AiO is to collect all important Nextcloud components under one hood - this is the reason why it comes with it’s own DB and there is no way to change it. If you need to you should check other installation methods e.g.
- docker-compose-setup-with-notify-push-2024 - other variants listed there as well
- Nextcloud docker compose setup with Caddy (2024)