The installation of v9.0.3 fails with various web hosts.

[BitRat]

Hello Prestashop developers and community, 

I run Prestashop on a web space at IONOS, a partner recommended by Prestashop.

Due to the end of support for PHP 8.1, I had to upgrade my version 8.2.4 to 9.0.3. 
First, I tried the one-click update, which worked at first. After the update, when I was in the backend/dashboard, 
everything seemed to be working fine at first, but when I tried to update the modules, the page froze, and after a while, I got error page 504. 
So I restored the backup from 8.2.4 and tested the whole thing again. After the second attempt, I tried clearing the cache first, but this time the page froze again and I got 504. 

I then tried completely reinstalling 9.0.3 in a different directory, which also took me to the dashboard, but then 
the shop froze again – 504. 
I had previously set the PHP version to 8.4, and the database was a new and empty Maria DB 10.

For all new installations of 9.0.3, I always deleted the entire database and also deleted the entire directory with rm- rf, then recreated it and reinstalled it. I tried this with all the databases offered, i.e., MySQL 8.0, Maria DB 10, and MySQL 5.7, but that is not the cause. The installation file is directly from the Prestashop download page. 


After ten attempts with various configurations, and with all adjustments to php.ini, and additional changes to the file and directory permissions, I then tried the whole thing on another webspace at Strato, but unfortunately the installation breaks down at the end of the installer with the message 502. 

Finally, I used the installation service from IONOS, where IONOS automatically installs Prestashop in a subdirectory with a single click; so I didn't have to deal with the installation or configuration, and the database is also created by IONOS.
The result was the same as with my own installation = The page freezes as soon as you change a setting in the dashboard. 

I contacted IONOS support and, after a long wait on hold, was finally connected to a hosting support representative. 
He then attempted the installation himself and failed. I was asked to document my experience in detail 
and send it to IONOS support so that the technicians/admins could take a look at it if necessary. 

As described at the beginning, the shop runs smoothly in version 8.2.4 with PHP 8.1 and MySQL 5.7.

I don't get any log files after the installation and the freeze.

What could be the reason for this?