in nodebb-plugin-dbsearch, query is $text - $search (not $regex).
I understand why.
Look at the readme of nodebb-plugin emoji:
To quote the relevant fragment:
The following emoji packs are known to be compatible with
To add custom emoji, visit the Emoji ACP page and click on the pencil button in the bottom left.
You just need to install the emoji pack you want and disable the current one.
Unfortunately, there isn’t a non-root method to change the emojis on the system level. You can only change how they look on an app-by-app basis. This means you can only change how they look when you’re using specific apps, but the emojis will not change on the system level.