404 not displaying, 302 redirect instead: can anyone else confirm this is standard behavior? …Or is there an issue with my particular configuration? I can’t test my 404 page in my local trellis vagrant dev environment OR in production, it’s 302 redirecting to the homepage when I type in a non-existing URL.
Sage 8, Multisite, HSTS.
Update: 404 is showing on subdomains, just not on the main domain…
Cheers!
Any plugins or code that might be interfering with this? Does it still happen on a blank install? Any idea what version of Trellis you’re using?
@ben thanks so much for the quick reply!
Upon further digging down the rabbit hole 
it appears that the issue is related to a known bug with the NOBLOGREDIRECT constant and the maybe_redirect_404 function (stackoverflow) that affects WordPress Multisite, complete with an outstanding Trac ticket (#21573) stretching back 5 years.
Solution? Add:
remove_action('template_redirect', 'maybe_redirect_404');
to a functions.php-include, or a mu-plugin (for better portability).
Sorry to spam the Trellis board; when there are so many moving parts you don’t know where to lay blame and, admittedly, I understand Ansible the least of all 
…