An example implementation of the ultralight html renderer into 1.19.3 minecraft using the fabric toolchain
Ultralight is a bit picky, and I can't explain it in full here, but the source code is very well documented. Everything is explained there.
Generally yes, but you might have to fix certain things if you don't use linux. I only tested this on x64 linux, your mileage may vary.
If you need to replace the drivers, the commit hash they're built on is 5011dbf. All files in src/main/resources/natives will be extracted at runtime, to a cache location, and provided to ultralight. All files in src/main/resources/ul-resources will be extracted as well, and provided to ultralight as resources.
You can just use the same setup for the most part, the HtmlScreen class is an example implementation of ultralight into the Screen api.
new HtmlScreen("file:///local/url.html") will construct a new HtmlScreen pointing to local/url.html, relative to the current working directory. I have no idea how to specify an absolute path, that's just a thing ultralight does, apparently.
Things like new HtmlScreen("https://google.com") work as well, but modern and complex websites (like youtube, steam, etc) have limited functionality when rendered with ultralight. Google works fine, except for 1 or 2 minor css fuckups.
Remember to cache the screens you create. You don't need to make a new screen each time you want to open one. You can just reuse the instance, and HtmlScreen is made to do exactly that.
To implement? about 4-5 hours
To actually get to a point where I've had enough knowledge to implement it? overall, about 2 weeks of research and fumbling around