I had a similar problem with the same upgrade (1.53.1 to 1.55.3) and was able to fix it. Not sure if it matters, but my os was at Debain 12 (bookworm), my php was at 8.3, and my nextcloud was at 29.0.9.2 when I was doing this.
Note: I’m new to nextcloud and this may have side effects that I’m unaware of, so back everything up first if you try this!
There was this symlink that seemed to be the issue for me /etc/apache2/sites-enabled/000-default.conf => /etc/apache2/sites-available/000-default.conf
I deleted the symlink, backed up the file, and then renamed the file to nextcloud.conf and created a new symlink to it:
sudo rm /etc/apache2/sites-enabled/000-default.conf
sudo cp /etc/apache2/sites-available/000-default.conf /etc/apache2/sites-available/000-default.conf.bak
sudo mv /etc/apache2/sites-available/000-default.conf /etc/apache2/sites-available/nextcloud.conf
sudo ln -s /etc/apache2/sites-available/nextcloud.conf /etc/apache2/sites-enabled/nextcloud.conf
I then re-ran sudo ncp-update and the update worked, after which, everything was really slow for like 30 minutes.
The newly created file/symlink was deleted during the update, but I didn’t have to restore my backup or do anything else. Everything seems to be working for me now.