The Joy of Manual Focus Lenses on Mirrorless Cameras

While testing the new Fujifilm X-E4, I had a lightning bolt of an idea: how would my Pentax DA prime lenses work on this camera? I have a 21mm, 40mm, and 70mm trio that I just love. If they worked on the X-E4, I could quadruple my optical options for it, and without spending a dime. The only catch would be manual focusing.