Catalina installs the same way as Mojave.
Tested with macOS Catalina 10.15 with OpenCore-0.5.7-RELEASE.zip (from April, 2020).
Note: Use create_iso_catalina.sh
for generating a macOS Catalina based ISO
image.
Notes:
Use 64-bit Ubuntu 18.04.2 LTS as the host for "best" results.
rm -f OpenCore.qcow2 ;sudo ./opencore-image-ng.sh --cfg config.plist --img OpenCore.qcow2