GIMP 2.10 now supports 32-bit files: suitable for creating TIF files for QTR?

See GIMP - GIMP 2.10 Release Notes

“High bit depth support allows processing images with up to 32-bit per color channel precision and open/export PSD, TIFF, PNG, EXR, and RGBE files in their native fidelity. Additionally, FITS images can be opened with up to 64-bit per channel precision.”

I just imported a 16-bit grayscale Photoshop file and GIMP retained the embedded 16-bit Adobe Gamma 2.2 Grayscale profile.

I haven’t tested more than that.

Is GIMP now a valid alternative to Photoshop ?

As of a few weeks ago I would say GIMP is finally up to snuff, yes.

It does linear curves too. I haven’t had the time to dig into it but hopefully will blog about it at soon.