I'm running Apache 2.4, and the directories in question (/tmp, /config, /lang) are NOT accessible through the browser. My Apache config includes location directives prohibiting access, e.g.:
<Location /tmp>
Require all denied
</Location>
I have verified that browsers return a 403 when attempting to view the paths in question, but Matomo's system check still returns errors indicating they're available through the browser.
NM, I'm an idiot--accidentally had enabled mod_auth_mellon (Okta) auth on the site.