I haven't heard of any official statement from PSG side interestingly. I didn't know that they already parted ways with Galtier. Because I check Transfermarkt frequently and I still see him as PSG's manager. Maybe they are waiting for PSG to announce the new manager officially soon to replace Galtier with him right after that.
The new manager is likely to be Nagelsmann for now. At least the latest speculations point to that. But I feel like they haven't still made up their mind between Mourinho and Nagelsmann options. Mourinho is still open for contract discussions with PSG. I find Mourinho more credible about bringing a Champions League title to this team honestly.
I wouldn't like to underestimate Nagelsmann but there is a really big career difference.
