Have you tried reading the docs?

https://docs.nextcloud.com/server/latest/admin_manual/configuration_user/reset_admin_password.html

Did you try

sudo snap remove --purge nextcloud

This will remove the data directory of Nextcloud. Alternatively you can check where snapd is creating this directory and remove it manually.

If you also have entered your email in Nextcloud you can try to reset your password over the mail. https://docs.nextcloud.com/server/latest/admin_manual/configuration_user/reset_admin_password.html#:~:text=Click the password reset link,to reset it for you.

Did you remove the snap with purge?

Like, sudo snap remove --purge nextcloud? Because the purge will (should) erase stopped passwords and stuff.

I have a snap Nextcloud that I’ve managed to keep alive for seven years now… I’ve had a few issues, but it’s been pretty good overall.

One day I’ll put up a Docker and move everything over… One day.

I don’t know much about the snap but you can use docker compose to stand up a deployment pretty quickly. If you aren’t super confident you could use Nextcloud AIO

This is a major reason to use simpler technology.

I can’t help you, but i had a similar experience with similar technology. I spent lots of time recovering content. I succeeded, but i have software development experience. I didn’t want a repeat of that.

In the end I picked windows file sharing for home networking and filebrowser for occasional access to data files from outside of home networking.

Web dav is a very good alternative. Apache web server will be easier, but nginx can be made to work.

Joplin is another good alternative, which is based on web dav.

You can pay around $2-$3 a month to shared services provider for hosted web dav.

Are you trying to recover data here?
Seems like you didn’t use it and (maybe?) don’t have data to lose here?