If the person has the logic and the abilities to do, than take no worries.

On the other hand, you will have to agree to start with a beginner's salary, and possibly to support freshly graduated engineers in their twenties convinced of being much more competent than you (and sometimes / often rightly so).

It is surely possible since it is a skill that can be acquired alone with a simple internet connection. Tutorials abound on the web. I met a lot of self-taught developers in my professional environment, and myself, I had already started to learn how to develop on my own before my studies.

Of course it is possible: as I said, it is the only sector where today there is no THEORETICAL barrier to entry.

I say theoretical because France nevertheless has its specificities: youthism and the diploma (in particular because of SSIIs which sell on CV profile) that is to say that if it is not a retraining desired by your own employer it will probably be difficult for you to get hired on a permanent contract. The diploma still passes if you were young but without diploma and age in addition, or you have a related diploma there it can pass in a startup if you become really very good and are an enthusiastic communicator young in the head (because in general you will be surrounded by young people).

On the other hand, nothing prevents you from freelancing around the world on the platforms that exist today (upwork being one of the best known). For that it is better to choose the best return/time spent ratio, today it is certainly a javascript framework like react or datascience in python (if for example you have a mathematician profile for the latter).

Once you've made your freelance niche, you won't particularly want to become an employee again;)