The unlikelihood that several other programs would be unable to open a file using something which has been standard for many years means there’s most likely an issue saving using PREDICTOR_FLOATINGPOINT in RawTherapee’s tiff32float branch. @Hombre hinted yesterday that maybe it requires using ADOBE_DEFLATE compression.
I created that image using probably libtiff-4.0.8, though ldd shows RT linked against /usr/lib64/libtiff.so.5 which points to libtiff.so.5.2.6, so… ???
strings /usr/lib64/libtiff.so.5.2.6 shows LIBTIFF, Version 4.0.8
Doesn’t help that the official website is dead TIFF Documentation
This one is less dead: TIFF Documentation