Welcome.
How niche we talking here? I like me some out there games.
Couldn't tell you what DTube expects, although with Vegas I've been using the Sony AVC which I think is some offshoot of h.264 (I remember having to do some really dumb file editing trick because this video editing unit I did for a laugh required .mov files for some reason but exporting .mov from my PC meant it couldn't play on the Macs there) with AAC audio. Haven't had an issue on my end with it. I don't know codecs well though, I just found that combination the least painful to render .mp4 files in Vegas.
Don't wanna necessarily plug my stuff but here's a link to a video that I'm pretty sure had those settings when I exported it, although that was a while ago but I just reuploaded to DTube.
Not on a Mac, but did see your video and I did get audio. Idk maybe Macs don't have LAME by default or something, wouldn't surprise me. I think DTube doesn't re-encode the source file if you are running it at the 'source' quality instead of 480p.
Well, niche enough that I'm often the only person within my circle of friends I know of who plays them. I've got some in mind to cover like Caves of Qud (a really nice post apocalyptic Roguelike). I've also got a video in the works for the best games for lovers of necromancy (I got a real thing for the whole summoner archetype in games, especially necromancy).
The next video should be much more entertaining than the first - and a bit shorter.
Thanks for your video link and your insights about the video codecs. I'll have to experiment a bit.