Thank you all for your replies, they're already helping me a lot. It seems that there is a process that takes place before changing the repo, which involves moving the executables (If I'm not mistaken.), and I'm not sure that this process was done on my computer (The executables seem to be duplicated? They are in both ‘/bin’ and ‘/usr/bin’, and the same goes for the other folders.).
I may be mistaken, so I will take the time to reread ‘A New Epoch Begins’ when I have more time. If this is what I understand, I just need to create this script at system launch, which performs the process, before I change the repo.
I am indeed still at the Shannon depot:
$ eopkg lr
Solus [actif]
https://cdn.getsol.us/repo/shannon/eopkg-index.xml.xz