I was doing the exact same thing this weekend! The answer is yes (I think).
I'm not on my Gentoo box at the moment, so I'm not 100% sure that I don't have apulse - I don't recall installing it, but I definitely don't have pulseaudio. The sound was working (with speakertest), but I had no sound in Firefox. I found a forum post [1] that said to find these two settings in about:config: browser.tabs.remote.autostart browser.tabs.remote.autostart.2 and set them both to false. For me, the latter was already false, but the first was set to true. And then the sound worked! Hope it works for you, -- Thomas [1] https://forums.gentoo.org/viewtopic-p-8118290.html (the third post)
