So, I'm trying to do something similar to https://learn.getgrav.org/content/media#audio-actions. For some reason, something seems to be adding quotes around the source tag.
Markdown:

Resulting in the following markup:
<audio controls="1" controlslist="nodownload nofullscreen noremoteplayback" alt="The Sound File"><source src="/user/pages/m4as/the-sound-file.m4a">Your browser does not support the audio tag.</audio>
but when I look at the rendereed HTML in Chrome Dev Tools, I get:
<audio controls="1" controlslist="nodownload nofullscreen noremoteplayback" alt="The Sound File"> "<source src="/user/pages/m4as/the-sound-file.m4a">" Your browser does not support the audio tag.</audio>
Note, the extra quotes outside of the source tag... it's like whatever is converting the < and > to markup is also adding quotes.