Gedit markdown syntax highlighting doesn't work

[eric72777]

Describe the problem: Gedit does not show proper syntax highlighting for markdown files with the default "Pop Dark" or "Pop Light" color schemes. The visual display looks the same as "Plain Text" syntax highlighting. Other languages (e.g., python) syntax highlighting works properly, and other color schemes (e.g., Classic) work properly.

Steps to reproduce:

1. Open a markdown file (e.g., README.md) with gedit.
2. Verify the syntax highlighting is set to Markdown on the bottom right of gedit.
3. See that all text is the same color.

Pop version: Gedit version 41.0, Pop!_OS 22.04 LTS Installed: 5.5.1~1657215006~22.04~6621efc

[isantop]

I can definitely reproduce this on Pop 22.04. It's not just the Pop style as well; Yaru also produces the same issue. However, I'm unsure as to the cause.

Just a note; the Gedit styles are handled in the pop-os/default-settings repo, rather than the theme. I'll get this transferred over there.