No syntax highlighting: only one text color and style no matter what theme

OS: Linux Mint 21
Guake version: 3.8.5-1 from Mint's repos.
The PPA does not support Jammy and I don't know how to compile stuff.
Repro Rate: Unknown. It works on my desktop PC but not on my laptop. Same version of Mint and Guake.

**Describe the bug**
On my laptop PC, where I installed Linux Mint 21 yesterday, Guake has no styling for its text. Check out this screenshot: https://paste.pics/I4MMD

I installed Linux Mint 21 on my desktop PC last week and the exact same version of Guake has full styling for all text, cf. this screenshot: https://paste.pics/I4MLK

**Expected behavior**
The Guake theme should highlight syntax.

**Actual behavior**
No syntax highlighting regardless of which theme I choose. All text has the same style and colour.

**To Reproduce**
1. Install Guake
2. Do a bunch of stuff in the terminal

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guake --support output:

$ guake --support

Guake Version: 3.8.5

Vte Version: 0.68.0

Vte Runtime Version: 0.68.0

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GTK+ Version: 3.24.33

GDK Backend: