I usually use the "auto connect" option. It works (debian 12.5) as it should. But I would like a browser add-on to be able to a) know that the connection is established; b) disable and enable the connection on a system-wide (not just browser) level.

It works as expected, it works on Windows better

It stopped working a few months ago (2024) ... It can no longer logged in... Firefox would launch the Nord VPN log in webpage, but after a successful log in, the Nord VPN Add-ons would still be asking you to log in :-(

Can't use this, since my organization is blocking VPN and I can't connect to a Obfuscated VPN in this app.

Nord was pretty good and fast, but...
Since last year their browser extension has been secretly throttled. This was confirmed with their devs after multiple emails to support. They never told us about this throttle and the website continues to advertise that they do not set any limits. Most likely their support even dont know about it and will tell you otherwise, which will just show how they can make such serious changes even without careful considerations within their team.
I gave some time to see if they will fix it but after a few months it didnt sound like they cared at all. If you are reading this you probably are interested in using the extension and not the desktop app, so my advice is dont get Nord now unless you are good with being slowed.

Update:
It is the case. Anyone can try to download a file and see for themselves it can never go above a certain speed. I see some previous reviews that mention this too. Just like I said pretty much no one other than devs knows about this.
Ticket 15039623

As of June 2024, this extension severely throttles internet connection speeds.

Using NordVPN without the extension is no problem at all, but the browser extension quite literally slows your experience to a halt. It's unusable. If you haven't purchased a Nord subscription yet, and you are hoping to make use of the browser extension, look elsewhere. All of the 5-star reviews for this extensions are likely out of date, and or posted by people provided with financial incentive to do so.



TL;DR
Steer clear.

Might not have gotten every security corner to work, but so far a pleasure