Turns out there was a problem with converting the .rpm package with alien.

I didn't include the --scripts parameter.

Here's how the package should be converted to .deb

sudo alien --scripts --to-deb oracle-database-xe-21c-1.0-1.ol8.x86_64.rpm

I nearly managed to make the configuration work but it is a hell to make it work on debian, I think I'll look for alternative distros on which run this database.

Here's an article that pointed me towards the semi-solution.

https://www.baeldung.com/linux/debian-oracle-database-express-edition-xe