Thankfully Cloudron allows access to all kinds of background goodies. In this case, what was important is the PostgreSQL db. So, off to learn to some psql commands!

I figured out I had to deal with two bits of info in two columns. The is_active column and the email_confirm_token.

Using the following I could UPDATE the is_active from 'f' to 't':
UPDATE users SET is_active='t' WHERE id='1';

I thought this would be enough to get me in, but when the login page was still asking for the email confirmation, I looked in the db and realized that the email_confirm_token still had something. So, I checked the earlier confirmation email, which was
https://myvikunja.install.com?userEmailConfirm=longstring, and replaced the longstring with the data still in the db column., and put that into the browser. Voila, I was then (re)confirmed, and could log in. Phew. I was really worried a good day's work was lost.

But, WHY this reset on my user??