I'm late to use mirrorless cameras, but recently tried using my father's old Nikon speedlight SB-24 and SB-80DX flashes with my Nikon Zf body. Miraculously, the workflow of putting the camera in manual mode and using the flash TTL exposure almost works.
The resulting pictures are great, but composing them is difficult, since the camera viewfinder shows the unlit exposure. (I'm impressed that in an almost-blackened viewfinder, the Zf's feature detection and autofocus work reasonably well.)
Is there a mode or trick for the Zf (or mirrorless cameras generally) to display an overexposed image for composition and use the specified manual exposure in the resulting image? Or is this just a coincidence that there's anything useful from pairing temporally-disparate technologies?