Thanks for your response @jc00ke! I wanted to follow-up here and tell a little bit about what I actually ended up doing.
I’m using live view to deliver my encrypted content to the browser, which then uses custom HTML elements to decrypt the content and render it on-page.
The form for creating new content is not a live view form.
The screen accepting new content has faux inputs where the user can write plain text, and see the decrypted version of their images, but the actual form inputs, which are hidden, end up being the encrypted versions of the plain text content. I use alpine-js to bind to the change events on the faux inputs, and modify the values in the hidden ones. Then I use javascript and the fetch API to submit the form over AJAX outside of LiveView. Then, the endpoint that creates new content broadcasts the creation event over PubSub, so all viewers get live updates anyway.
Initially I tried using a LiveView form and just setting the content with Javascript, but I had a difficult time getting Live View to behave predictably when I was setting input values through JS, rather than plain user input. The traditional form cleared of all of the strange inconsistencies I was seeing.