Apple announced in mid-2014 that it would discontinue Aperture when the new Mac OS X Photos app was released what actually happened in April 2015. Now she's hammering the last nails into the software box.
In a new support article, Apple now reports that Aperture no longer runs on MacOS Mojave's successor. It simply cites “technical reasons” for this, but most likely it has to do with the fact that macOS 10.15 leaves out old libraries and is totally 64-bit.
For Aperture orphans, the simplest option of all to migrate to Photos is that in this case we are talking about a much more basic manager. For those who want something similar to what Aperture was, the best alternative is even Adobe Photoshop Lightroom (to which this one who writes to you migrated in 2015).
Aperture was for photos like Final Cut Pro X for videos. It's a shame that Apple decided to kill him.