sndio audio on Void Linux not always available in browsers.

I am trying sndio again, on a fresh install of Void Linux (rolling release).

$ cat /proc/asound/cards
  0 [Generic        ]: HDA-Intel - HD-Audio Generic
                       HD-Audio Generic at 0xd05c8000 irq 82
  1 [Generic_1      ]: HDA-Intel - HD-Audio Generic
                       HD-Audio Generic at 0xd05c0000 irq 83
  2 [U192k          ]: USB-Audio - UMC404HD 192k
                       BEHRINGER UMC404HD 192k at usb-0000:08:00.3-1, 
high speed

I am using my Behringer USB sound card as default.

Not much information on the subject, and it has been some years since I 
tried sndio last, and couldn't remember what I did with the sound card, 
so I asked Google's AI. In the end, a configuration that seemed to work 
is the following:

# touch /etc/sv/sndiod/conf

# echo 'OPTS="-f rsnd/2"' > /etc/sv/sndiod/conf

This seemed to be stable over a number of system restarts, using both 
Epiphany and Waterfox. Most of the browser audio is either connected 
with YouTube, or tomplay.com. The later apparently uses audio over web 
for backing tracks to it's music scores. Unfortunately, Waterfox has 
started not cooperating with either service, while Epiphany seems a bit 
more consistent. It should be noted that alsa-lib is installed on my 
system, but not alsa packages. Sndio is the only audio server.

I am first and foremost interested on getting feedback as to whether 
creating the conf file was the recommended way of getting my USB sound 
card as default audio output source, but also any other advice that is 
relevant.