I obtained a similar effect with The Gimp and the wavelet decomposition plugin[1] that splits the picture in various layers containing details at different granularity. You can then simply remove the "bad" ones. On portraits, you can remove freckles and wrinkles very easily this way, too.

[1]: https://docs.gimp.org/2.10/en/plug-in-wavelet-decompose.html

So I tried it on his image and here's how it looks with default settings:

https://demo.intellique.org/nextcloud/index.php/s/SsgWGczo6G...

Much less work :)