Disabling webaudio breaks the Matrix Element web client

[mpeter50]

In a (not so) recent update Element started to break on browsers that dont support the webaudio API. The webapp will present a warning that the browser is not supported, and when the user decides to attempt to use the webapp anyway, it immediately shows the failure page

Compatibility warning page	Failure page

Setting dom.webaudio.enabled to true in about:config solves the issue without browser restart.

The Element team will not fix this issue. (element-hq/element-web#27864, note that the issue title is misleading, the problem was the config value, not the FF version)

However, maybe there is more we can do besides blaming Element, and the broken misconfiguration page that still doesnt tell you whats the source of the perceived incompatibility (turns out this was a misunderstanding, this was not intended to be done).

According to arkenfox/user.js#1194, webaudio was not a major source of fingerprinting back in 2021, and according to a later issue that referenced it, arkenfox/user.js#1701, in 2023 Firefox 118 was still working the same way, if not a little better.

I think it would be worth considering to change this tick box to default off, in the "Website Tracking" category: