A user, Don, shares a hack to customize the offline indicator in Discourse by modifying its template to include icons. Initially, the hack combined two separate icons (wifi and slash), but Don later updated it to use a single Google Material Wifi Off icon via the Discourse SVG and emoji CSS helper, avoiding the need to merge icons. The changes are available in a GitHub repository: discourse-offline-indicator-hack. Lilly praises the approach, calling it a “cool trick.”
Hello 
This is a small hack (redesign) to the official offline indicator.
Site Setting: enable offline indicator
I’ve override the offline indicator template to add icons to it. To add the icon, I put the following two icons (wifi and slash) each other.
Default
Modified
Here is the repo (you can use it or use as template if you have other ideas): GitHub - VaperinaDEV/discourse-offline-indicator-hack · GitHub
Nice! I love how you combined icons - cool trick! 
Hello
I’ve updated the theme component because now the offline indicator component is a .gjs so we can’t override it’s template.
I use the Discourse Easy ‘SVG Icon’ and ‘Emoji’ in CSS helper. I’ve added the Google Material Wifi Off icon. So this way we don’t need to merge two separate icons.
https://github.com/VaperinaDEV/discourse-offline-indicator-hack/pull/1