I just decided it was time to list Rhapsode alongside Lynx, Dillo, and NetSurf as a smaller engine you can help grow by making sure your pages look (or in Rhapsode's case, sounds) decent in them.
But definitely, test in Firefox and Safari/Midori/GNOME Web/Odysseus/etc too! Whatever you do don't just test your pages in Chrome, I fear a Google monopoly.
Here's my other asks: https://odysseus.adrian.geek.nz/developer/web-bloat.html
In Rhapsode's case specifically, you should be:
1. Writing semantic (X)HTML5
2. Declaring your page's language
4. Avoiding excess text
5. Making sure your site's fully navigatable without it's navbar
Though you can go further if you want: https://git.nzoss.org.nz/alcinnz/rhapsode/wikis/CSS-Speech-Tutorial
This helps Rhapsode to give it's most engaging monologue, whilst allowing your readers (once I implement the vital feature) to navigate your site.
I find Firefox is the best for testing anyways. Chrome has the better dev tools, but Firefox handles caching slightly better.
For people who care about, support, or build Free, Libre, and Open Source Software (FLOSS).