Andrea, ffplay always works this way for me and always has.  So I just use ctrl+c.

Yes; trying a render with x265-10-bit and playing back the file
obtained with ffply I get a freeze in the last frame with the last
line of the terminal (indicating the momentary value: 19.46 A-V ...)
that keeps increasing the number to infinity and I have to stop with
ctrl+c. The same thing happens with DNxHR and x264.
See image.