A toggle is not the best solution to your problem.

100% correct. Unfortunately I'm far more likely to have access to a toggle than for them to make their dark mode nice.

E.g. I've asked them to add more languages to the code button in their WYSIWYG editor for replying to tickets. I don't use/do any web stuff but I had figured out that they use Froala, and Froala uses prism.js. I asked them to include 5 more languages (bash/sh/shell, batch, ini, json, Powershell) and requested that the list be sorted alphabetically, and told them it should just be a matter of changing the Froala codeSnippetLanguage plugin option. I haven't even had a reply in 5 months.

I also spent some time trying to modify the WYSIWYG editor options myself using a userscript but didn't get anywhere useful.

I understand the annoyance of just having the list of requirements without having vendors, models, etc as it puts the burden of effort on the reader.

On the flip side, the list would be crazy and more work for the devs, plus the definition of "most popular phones". Having that list would be informative but I don't know that it would be that helpful considering it wouldn't make a difference with regards to the devices that Graphene supports?

It probably wasn't clear in my post but I'd be happy with the toggle being in the browser (not something I've historically thought about but a great idea), it was more about the existence of a toggle.

I do agree with @jaredwhite@humansare.social that having the toggle in the header is a waste of space. Same with horizontal tabs.

Do you mean altogether unnecessary, or unnecessary as a persistent toggle on the main screen?

If you're talking about the former I'd disagree, easiest way to explain is with my own real-world example.

I put basically everything in dark mode, but our ticketing system's website I put in light mode (even though they have a dark mode) because their dark mode looks like shit.

Searching would probably have been quicker than commenting :)

https://grapheneos.org/faq#future-devices