Dark Mode always on, X.com, Twitter, IPad using Safari
When using X.com (Twitter) on my IPad, using Safari browser not the app.
Dark mode was always on, irrespective of time. So I had Twitter tabs in dark mode and other tabs in light mode.
I sorted it after much rummaging around. See screen shots, numbered 1 to 5, they may display out of order. Hope this helps someone.
iPad, iPadOS 18