Registax, Helicon or other focus stacking software isn’t a needed ‘extra’. I just did a 10 JPG image focus stack of the moon, and unlike many different versions of Photoshop that kept complaining not enough overlap, Affinity lined up each image, stacked them perfectly.
And the good news is that since Affinity is 64bit, you aren’t restricted to image size like in Registax, which is 32bit (it’s Freeware, and works wonderfully, but that 32bit limit can cause stacking failure) It imported and stacked 50 RAW files flawlessly. I watched as it stacked the image, bit by bit. No ghosts, no mis-aligned areas.