YES! I finally did it and achieved a partial win over #peertube.
I have been battling to have my videos support HLS and other modern good things, but it seems like the only way to this currently is to use a patent-covered codec from 2003 (H.264/AVC) until something like DASH is implemented, which at least supports VP9. Anyway, I digress..
After patching Peertube into "Do NOT touch my streams" mode, the resulting videos have been extremely wonky to put it mildly, jerky and pixelated, so it's been several days of uploading and deleting to find something that works. And while I had pretty much resigned and figured that this is why we can't have nice things, I tried a few desperate last attempts, and suddenly it works.