Deleting a validated invoice in odoo

I generally tend to stay away from administrative software: I find it way too complex and severely overengineered, most likely because I don't know the subject. The only thing I did in the past is to choose and deploy an application for my administrative. I picked odoo because, between all the candidates, it seems to be technically well done (python-based and easily deployable with docker) and with the biggest developer community (by a large margin).

During the years of tests and errors, I ended up having some hanging invoices that must be deleted. Their document number is not an issue because they are the last ones in their own year (the ones in the middle have been reused and recovered). Most of them have been deleted without any issue but a couple of them has been previously validated, hence odoo refused to delete them. I tried to put them in draft mode, delete all the contents, remove journal entries... nothing changed, still the same error.

Looking online for a solution, I met a bunch of useless threads suggesting why you should not do that. Well, thank you for nothing: I still need to delete them, regardless of what you think. So at the end those documents were hanging from years, staring at me and laughing.

But recently I found a hidden comment at the end of an odoo thread where PeaSch says: