Nextcloud File Location

i have an orange pi with ubuntu server and umbrel installed on a 32 GB SD. via umbrel i have installed Nextcloud.
I would like to make sure that the files uploaded to nextcloud are stored on a second 256 GB EMMC disk. is this possible?

Here’s a great guide here that should be a great hand to you

i followed this guide but when i try to start nextcloud from umbrel i can no longer login with my credential and nextcloud ask me to create an admin user.