I found this article about the tax. In good news the NFP who are proposing this change are short of a majority, and need agreement from Macronist in parliament to get it passed. Which probably makes it unlikely to be realized. But yes, more exit taxes are to be expected broadly.

https://www.connexionfrance.com/practical/what-is-exit-tax-that-frances-pm-candidate-wants-to-bring-back/674399