In Firefox, setting privacy.resistFingerprinting = true in about:config fixes the canvas leak and possibly the audio leak. It's part of a push to bring into Firefox privacy features from the TOR project.
I really want to do this, but last time I checked it also leads to FF sending UTC time back to sites (or something like that), resulting in showing non-local time for your own and other interactions on pretty much all sites like github/slack/... Fairly annoying. I hope this becomes a separate setting at one point.
I enabled it and Todoist would show me a dialog on every page reload to set my timezone to UTC. After I realized that resistFingerprinting was causing it, I had to disable it.
It would be nice if the settings inside resistFingerprinting were configurable. I understand that the point of it is to make every browser look the same to analytics engine, but having timezones and zoom levels reset is not the best thing.
https://wiki.mozilla.org/Security/Fingerprinting