If you understand German, then I recommend the review by Mike Kuketz (https://www.kuketz-blog.de/briar-anonymitaet-und-sicherheit-...). Maybe you get a decent translation with Deepl, though I stay wary.

There is also a comparison to other messenger systems on https://www.freie-messenger.de/systemvergleich/. They have a PDF in English available, but it doesn't really tell much.