OK, here are a couple of things.
Affinity's nondestructive lens blur filter works in 32-bit but includes few options. You can apply a depth pass as a mask but you cannot control the focus point. Also, prepping the pass is hit-or-miss, for example there is no way to automatically equalize it to bring the densities into a workable range.
In comparison, Photoshop's lens blur is destructive (make a duplicate layer first) and works only in 8- or 16-bit. But you can use the HDR Toning panel to equalize the depth pass before converting it. The depth pass can be inverted in the lens blur panel, and you can easily specify the focus depth.
More seriously, Affinity has color samplers but they display values only in the 0-255 range, even for 32-bit images. Which is useless. I found several requests to fix this in the Affinity forum, some going back a year or two, but no satisfactory responses. This could be a show stopper.
Still playing . . .