I meant: The raw HTML isn’t properly parsed anymore with the latest version, hence you are just seeing the HTML dumped instead of rendered.
Yes, .gjs file indeed indicated a glimmer component, but the used method of registerConnectorClass in it won’t work (anymore)/
This is fully understandable. What Using Plugin Outlet Connectors from a Theme or Plugin essentially is saying is that, to render information somewhere on the page via that registerConnectorClass method , the way your footer.html file did, we now use a specific element, called a plugin outlet. For a footer, the above-footer outlet would work well.
It’s probably a good idea to read through Beginner's guide to using Discourse Themes and Developing Discourse Themes & Theme Components
It can also help to have a look at a simple theme component, to understand the structure. For example: GitHub - discourse/discourse-minimal-footer · GitHub
And finally, the Discourse bot might be able to help you a whole end of the way: it knows Discourse patterns well so you can give it your current code, explain the issue, and ask it to help you refactor it.
If you absolutely don’t feel like tinkering with it, the last option is to make a topic in Marketplace for some paid help.
But it’s really a very small component so I personally would advise to start with setting up a new component via our template, and figuring it out with the help of the bot.