Gantry5 child theme not recognized by grav admin

I've installed grav-admin, gantry5 and the helium theme, gantry and helium through bin/gpm. This seems to work fine, both site and admin. Then I created a child theme of helium through bin/plugin gantry5 child-theme. However my child theme does not appear in the grav admin themes page: it only shows quark and helium, both inactive. This happens whether I created the child theme with or without inheriting outlines from the parent.
If I set pages / theme: [new_theme] in user/config/system.yaml, then the admin gantry5 page recognizes the new theme, and setting styles in that page is reflected on the site. However grav-admin still shows only quark and helium both inactive.
Is that normal? Should I file a bug report?

This seems to relate to a bug:
https://github.com/gantry/gantry5/issues/2395

Hi @nfortier,
I've had the same issue with my child theme from Gantry Helium. After looking for a lot, I've discovered if you remove "Child" from the following code line in blueprint.yaml (- { name: grav, version: '>=1.5.10' Child }), it works fine.

Original code line (blueprint.yaml)

dependencies:
  - { name: grav, version: '>=1.5.10' } Child

Modified code line (blueprint.yaml)

dependencies:
  - { name: grav, version: '>=1.5.10' }

I hope I've helped.