Nextcloud - incomplete official information about installation

I know that this is a free service and that’s probably why it’s not fully developed.
But this is not serious.
For 5 hours I have been trying to install next cloud on RPi using the available guides. Did not work.
First tutorial:

This is funny, nothing happens after installation, the web panel doesn’t exist.

Second tutorial, this time installing a “clean” image:

After completing each step, I cannot log in to the www panel.
Ip address with port 4443 returns the wrong page.
Ip address without port 4443 shows the page with passwords and activation.(Nothing in the manual about this)
Once activated, the www panel starts working, but none of the password from the previous page matches. The default password is rpi also does not fit.

From now on, everything becomes unclear, I have 2 passwords that I cannot use, the desire to keep data on such a cloud is no longer safe for me.

Is it serious? Do you want to be user friendly?

I just moved it in the NCP section since you gave a bit more information regarding this solution.

So I suppose you found the IP address of your raspberry PI in the local network.

What do you mean by that? What is the wrong page? There is also a follow up with the configuration:
They also give alternatives via SSH or directly on a connected screen.