Instead of recompiling, I downgraded unison and unison-gtk with Bionic Beaver packages. There is no dependency issues.
Warning: you will not have any security update. https://packages.ubuntu.com/bionic/unison https://packages.ubuntu.com/bionic/unison-gtk -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1868502 Title: Synchronization with earlier Ubuntu versions or a recent Debian version fails To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unison/+bug/1868502/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs