I don’t like to compare Anvil to Squarespace or WordPress because those tools are great to build websites with little or no coding and little or no flexibility, while Anvil is great to build a web app with at least some Python coding, at most lots of flexibility.
Anvil is good at making things easier, and that sometimes introduces some limitations, but I would never ask to add more limitations.
I don’t know what you need HTML for, but here is another post that might be useful for you: [DONE] Seeking: a Rich Text display - #12 by stefano.menci
Here is the documentation: Redirecting...