I can't get this to work, I copied cascade.css and custom.css to '/www/luci-static/material' (and I'm sure they copied fine as viewing them through ssh show they are the modified versions).
Tried restarting the router, changing to another theme and back to material, and accessing luci from another browser, and I still see everything in the original light theme
Interesting - but in reality, my router is in a funky state at the moment. brought the internet down twice yesterday trying to fix it, much to my teenager's delight!!
You need to clear your cache of your browser. I dealt with this when making my own, every time I made a change I had to clear my history and cookies to see it
Yeah, cleared cache, tried incognito on chrome (did that before anyway), and even tried on a clean Firefox profile and no changes, still a light theme.