Well, the subject is nearly enough, I think... 😀

I'm looking for an accessible Markdown plugin for my WordPress blog. When I say "accessible", I'm mainly referring to the plugin settings, since the majority of plugins I tested are more or less useful, but quite tricky to setup; just to give an example, a lot of them use custom checkboxes undetectable by the screen-reader, so it's impossible to be sure if the option is active or not.

Any suggestions?

IF you switch to the classic editor, it lets you use markdown. Idk if the blocks one supports it or not. I switched to the classic one, and used the # ## to do markdown and called it a day. Unless is there something in specific you're looking for?

Well, I do need some more advanced features, as task lists, footnotes, code highlighting, etc.

you need a pluging for wich wordpress going to interprete the md files or a plug-ing to write these files?

Preferably a plugin which will interpret the Markdown in the editor, because that gives me a more consistent work process.

Maybe a bit off-topic, but I recently switched from Wordpress to Grav:
https://getgrav.org/

And it's a very fancy experience. Well, as far as you don't mind some templating and digging through configuration files. It's certainly not a one-click thing, at least I was very unsatisfied with the proposed blog skeletons, so I made my own.
But you get a lot of customizability in your hands in return, and as soon as the skeleton of your website is in place, it's just about adding markdown files.
You can even host everything in a git repository and version, since the system doesn't need any database, and even configure auto-deploy on your GitHub, so whenever you push changes they will be automatically delivered to your site as well.

That's a nice suggestion. I'm using Pelican (a static site generator made with Python), and it's really fantastic for some usage cases. But WP is far more extendable, that's the primary reason I'm using it on my main website.

The good thing about Grav is exactly that it's not a static site generator, like many other markdown website projects.
It's a full-fledged flat CMS, where you define the frontend of your website using markdown and twig templating engine, and backend functionality in PHP either written by yourself, or utilizing the rich palette of available plugins. The latter is often the case as far as you don't have very special requirements, so you just install all the functionality you need and play with markdown and templates.
It's thus not a problem to have things like a search bar, comments section, captchas, etc. all in very fine-grained control, in a system built around markdown, yaml, and folder structure.
Indeed, the palette of extensions can't possibly compare with the platform making up fifth of the Internet, so if your requirements are very special in this regard Wordpress will be better choice.
Also, while Grav is absolutely awesome, it's not a one-click solution, which may be a problem depending on how much energy are you willing to invest into building the website.
So, I'm mentioning it just in case.
Back when I was looking for Markdown plugins for Wordpress, interestingly, there were not really many of them. The one I used worked sort of out of the box, I didn't need to configure anything and I suppose if I wanted to modify something about the appearance, I would have needed to look into how Wordpress handles CSSs.