I have built static binaries of Unison 2.48 for ARM  and x86 64bits. Run on my NAS, the arm architecture is necessary to synchronize with the latest Ubuntu. The x86 is useful, eg to synchronize with older Ubuntu releases:
I will not support these binaries
I will not answer any questions or request on these binaries. I have built them for my personal use and put them online in case it might be useful for others.
|||Following instructions on http://www.crutzi.info/unison/binary/armel|
Remark on backward compatibility
Why don’t the Unison devs ensure compatibility between minor version of Unison?
Breaking compatibility is bad practice, in particular between minor versions. It breaks the trust that users have in updating the software. Programmers complain that users always run old versions of OSs/libraries/programs, but this is explained by the fear of stuff breaking during upgrades.