[15.0 -> 16.0] Cannot load the web interface after upgrade

[Saphar]

Module

Assuming the problem is with the web module.

Describe the bug

I am trying to upgrade my database from 12.0 to the latest. I managed to climb up until 15.0 and seemingly it is working well, but there is no way to make it work on 16.0. After any attempt to upgrade, even running the script without any errors, I always have issues loading the web interface. First there were problems with the "assets", these errors I detected in the logs already and seemingly were caused by upgrade issues with other module. Upon fixing these I was able to upgrade to version 16.0 without any errors. Then I updated all the installed modules. But I cannot get past the login screen. After login it tries to load the /web and it fails, in the console I see the error message "odoo is not defined". It happens even if I upgrade an empty database or if I create an empty database on version 16.0.

To Reproduce

Affected versions:
16.0

Steps to reproduce the behavior:

1. Upgrade from 15.0 to 16.0