Thank you for your analysis. I will share the most likely counterpoint for people to consider:
I think it’s probably fair to argue that on Linux you should be aware of what you are installing and what those programs are doing. A kill switch in this scenario that applies to the default network configuration is mainly going to protect you from random disconnects, while an intentionally misconfigured program set to bypass the kill switch by binding to a specific interface could be considered out of scope for what a mere software kill switch has to be doing.
This is compounded by the fact that the way to implement a kill switch on Linux is highly variable depending on distro and network configuration, there isn’t a single system API to plug into like on Android. In some sense if you are going to be performing sensitive tasks on Linux then you need to configure them properly, and if you don’t trust yourself and/or the application you need to be using the tool for the job that prevents this problem by design, which is Qubes.
Like I said, it’s an open question I’m presenting to everyone here, and I don’t really lean towards this argument one way or the other. I think…
…is also a perfectly valid opinion to hold, and if this is what we want to say then we could still de-list Proton. I don’t think it’s unreasonable to instead simply add a warning about this edge-case either though.
FYI: The rest of your post is frankly so off-topic to the Proton discussion we’re having in this thread, that if I were you I would not be surprised to see moderation action if you try to derail the Proton discussion with NextDNS complaints or organizational questions again.