More than 45 years ago, I used to operate a Durst Miniprinter semi automatic mini-printer.
IIRC, each time I switched film formats, I would have to turn out the lights on the darkroom side, open the light-tight doors at the back of the housing, reach in and grab the removable lens mount with the existing lens on it and switch it with the lens mount with the new lens on it.
Followed of course by closing the doors before turning the darkroom lights back on.
Here is an internet image showing someone from the 1980s using a similar Durst unit: