Processing a photo of the Milky Way taken with an equatorial mount

Hello everyone.

I've just finished shooting (63 exposures) the Milky Way in the south of France under a beautiful Bortle4 sky!

I've aligned and stacked these images with PixInsight and the result isn't too bad (see image).
My problem, as you can see, is that the foreground is completely blurred... normal, it's taken with an equatorial mount with tracking... Yes, the earth rotates...

I do have a foreground image (one of the subs I've been able to obtain, cf 2nd attachment), but my problem is that I don't know how to replace the blurred foreground with a sharp one... I've read here and there that you could do this with Photoshop, but I haven't found a tutorial yet...

Do any of you have a method for reintegrating the foreground? (Maybe via a mask ?)

Thanks in advance.