If you upgrade to macOS 10.15 ‘Catalina”, be aware that a new install of Ortelius 2.2.3 will fail to validate through the additional security checks this release imposes. If you already installed Ortelius before upgrading the OS, it will run normally.
We do have an update in the pipeline to address this issue, but we have run into some other difficulties that Apple have imposed on us in terms of validating applications not sold through the App Store. This has delayed the update.
If Ortelius is critical to your work, we suggest NOT updating to macOS Catalina at all at present. It seems to have some severe issues for some users, regardless of which apps you use.
If you already have Ortelius installed, you can run it normally with Catalina, though we recommend Mojave (10.14) for the time being. Only new installs on 10.15 “Catalina” are a problem.
Another option is to run an older version of Ortelius, since apps compiled before June 2019 are given a free pass with the new security checks. For example, the previous release of Ortelius can be downloaded here: Ortelius 2.1.2 Download. This version lacks support for Dark Mode, but will otherwise run with all features on Catalina.