0.18 is now officially available. I expect it will be a few days as instance owners test the upgrade and decide whether or not to switch over. Especially since the captcha fix isn't coming until 0.18.1.

Relevant to this community is the fact that this upgrade includes two different PR's (1, 2) that add a number of semantic classes and ID's to the markup to aid in the creation of custom themes, userscripts, and browser extensions. Additionally the UI has been upgraded to use Bootstrap 5.

However it should be noted that Desallines has explicitly stated that there is no official support for anything utilizing these classes, and that the UI framework is going to be changed in a future update.

This means you're targeting these classes/ID's at your own peril, and they may break in a future update. They want to keep theming as light as possible rather than adding lots of custom hooks that people will then become dependent on and expect ongoing maintenance/support.