Apologies for the delay. Due to an eye condition I use dark mode and other accessibility tools all the time, it's not a nice to have.

On mobile devices I use the browser with the dark mode rendering flag as IBJoel described, along with a the OS being in dark mode.

The browser being set to dark mode rendering on the FT mobile site is perfect, it works really really well, and nothing "disappears" that I notice. Using the dark mode rendering on many other sites some web components often become difficult to see on the page, radio buttons and toggle switches are often the worst offenders.

On a Windows desktop I don't use the browser dark mode rendering or any specific app and it's dark mode, and instead I use the accessibility tools and switch Windows into high contrast mode (LeftShift + Alt + PrtScn, on a laptop your PrtScn might also need you to press Fn). This does everything in one go, and is a very consistent experience. Colours get stripped and changed but for me it works nicely, there are still some things that are awkward, radio buttons and toggles are again the baddies.