I also used Focal for years, worked well but was cumbersome.
There was a method published years ago that sounds crazy- but it works and is easy. I can not find the original posts to give credit.
Basically you lock your camera down and confirm sharp focus in live view, manually focusing on a chart or something with really good contrast.
Without moving anything, switch the lens to auto focus- but do not change focus. Look through the viewfinder, the in focus light should be solid. Then go to the af fine tune menu. I will assume it is at zero. Put it at +1 and hit enter, is the auto focus light still solid? Then +2, etc until the auto focus light starts to flicker at all- or goes off. Write down that number, lets say +4. Then go the other direction, -1, -2 until the focus light starts to flicker or goes off again. Lets say that is at -8. Average the two values together. -2 would be your final value. Whole thing takes about 2minutes, and my results were very very close to focal- which took a lot longer. Give it a try. Again, not my idea but I can not find the original write up.
By the way, I agree the mirrorless cameras just seem to focus better- when they achieve focus it is really sharp.
Gary