You are right, I didn't phrase it correctly, what I is meant that since Nougat I'm not aware of way to force system-wide use of a user certificate without gaini

You are right, I didn't phrase it correctly, what I is meant that since Nougat I'm not aware of way to force system-wide use of a user certificate without gaining root access. Thanks for the Firefox tip as well, it's been a while since I used Mitmproxy and I see things have not become easier since.