You might need to click on More info in the Windows Protect your PC screen, and then Run Anyway to run the CrossMobile installer.
.appimage and make it executable following either of these steps:
- In Nautilus (Gnome) or Dolphin (KDE), right click on file → Properties → Permissions → Execute: Allow executing file as program or Is executable
- In terminal, type this command:
chmod a+x CrossMobile-*.appimage
.dmg file as usual.
For more information please advise the release information here.