I am just now trying to use the multi-lang filter for the first time, using Moodle 3.3+
My default editor was TinyMCE. I found that when I put in <span lang="en" class="multilang"> in the code window, that the editor removed it as soon as I saved the page. When I switched to Atto editor, it did not remove the <span lang="en" class="multilang"> tag, and the multi-lang filter worked as it should.
Was I just missing something, or should I post this to tracker?