I have been following this topic for 2 years ...
I have been using Affinity for the last few years & I am very happy with it BUT allot of my work requires me being able to generate a TIFF file with CMYK + spot channel for white. This is for printing with UV printers which not only print the CMYK colours BUT also white. Everything I do depends on it. Being able to create spot channel in PDF doesn't help me at all.
Is there a patient issues which stops affinity providing this option?? If so, it would be understandable BUT it would be nice if you let us know so that I can find another option. it is really a shame that affinity cannot do it.