Louna It's illegal for anyone to not accept your IBAN for a direct debit or for paying a salary etc. -- even if you don't have an IBAN from the same country. If you experience any issues, make sure to report the company/merchant: https://www.acceptmyiban.org
Of course, even with the legislation bunq wants to minimize any friction and opened branches in multiple European countries. You might want to send this entry at Banque de France to any company that doubts that bunq has a local presence in France: https://www.regafi.fr/spip.php?type=simple&lang=fr&page=af&id=1960 But not sure if that is convincing to any company that is already breaking the law.
Je peux enfin en faire ma banque principale ?
That is, ultimately, for you to decide. I'm from Germany and I use bunq as my main bank since many years. I still use the original NL IBANs and have not fully switched to DE IBANs, because I do not see the need. If there is a problem with a company, I just report them to different governmental institutions here in Germany (of course first I ask them nicely to rectify the issue and teach them about the law), but as of late I seldom have any issues anymore. Most companies have no problem with accepting my bunq IBANs, both NL and DE.
The situation in France might be different. And not everyone wants to complain when something is not right, they just want things to work right out of the way. So if you want to use bunq as your main bank or not, you have to decide yourself. Rest assured that bunq is doing as much as they can to make sure their French customers have a good experience.