Concatenate two video files with a dip to white with FFmpeg
Assuming input0.mkv is 10 seconds long:

ffmpeg -i input0.mkv -i input1.mkv -filter_complex "[0]fade=t=out:d=0.015:st=9.985:c=white[v0];[1]fade=t=in:d=0.015:c=white[v1];[v0][0:a][v1][1:a]concat=n=2:v=1:a=1[v][a]" -map "[v]" -map "[a]" output.mp4



Note that using your values with typical input frame rate will result in only a few frames being white which will appear as a flash instead of a dip to white, so I recommend increasing the fade duration.
All inputs must have the same parameters (width, height, etc).
See FFmpeg Filters for more info on fade and concat.