I would think that if it had access to those in the discord app, it would still be able to do so in the web browser, but now it would ask for your permission.
I have never used such devices, but I assume that either they appear as normal audio source devices in the system, or voicemeeter makes one for them.
at the same time its ridiculous how limited voicemeeter is regarding the number of audio devices it can handle. its an artificial limit, even in the paid version
what do you base that probably upon?