Server reached via Webmin’s server index:
No navigation menu when first accessed that way. Only upon going into theme settings and simply saving does the side nav appear as it should. Steps to recreate are to simply click on the server icon via that index in the base Webmin instance, or alternatively choose from the dropdown of available servers. Either way, it’s the same.
From where do you want those theme settings files? The base webmin, or the ones accessed?
And to the best of my knowledge, i’ve not met @jet438 
Using firefox here on Windows 11. That said, tried in in Brave, got the same result, as well as in Edge.