Supply of Raspberry Pi is a central problem for Openflexure. It was originally chosen for the wide availability and camera integration. Now that Pis are so hard to find, alternative platforms look better, but the camera integration that gives the lovely flat background in microscope images means that there is significant development required to port the software to other platforms. Even now the server is not running the latest Pi operating system because of major changes to the way the Pi camera is handled.
There are a couple of work-arounds:
A Pi4 will give the slickest interface if you are using the raspberry Pi desktop. However if you have almost any older version of a Pi it can work, particularly if you install the ‘Lite’ version of the Raspbian Openflexure operating system and then operate the microscope from a remote computer. You will probably need SSH on a local cable if you want to set up things like wifi. The minimum Pi then is stated as Pi1 B+, 512MB. That should actually mean that it will run on a 3A or a Zero 2.
You could use a USB camera, but with a Deltastage you would also need to write something to control the motors directly over serial as it is not really possible to us a Deltastage manually.