I’ve kind of tuned the VR experience as best I can with my PC and Rift S, and I’m not sure our bug reports are going anywhere, so now I’m just trying to have fun. 
What I do to capture these is use the Xbox Game Bar (windows key + G). The shortcut to go directly to recording is windows key + alt + R. Then, if your headset mic is set as the system default input (which mine is when I’m in VR thanks to Oculus Tray Tool), when you enable to mic input on the recording widget that pops up, it records your mic audio on top of the game audio. If you don’t want any mic audio, you don’t need/want to enable the mic.
When you’ve gotten your desired footage, you can click the stop button on the recording widget (which is visible on your monitor but not in the recording) or you can use windows key + alt + R again to stop the recording.
Once you have the recording, the problem is that it is both eyes, side-by-side, and usually has a lot of swearing and muttering and failed parts (at least in my case). So, you need to at least edit it down and, ideally, crop out one of the eyes. Then, even harder, you have to figure out how to make it all fit in 5MB! That means 20-30 seconds at most and compression.
I use a freeware program called “Shotcut” to take the captured footage and edit it. I can just drag the footage into the program, use a source cropping tool to crop out one eye, cut it down to length, boost the audio if necessary, and then encode it into an .mp4 file, adjusting the compression to try to get it to be 5MB with somewhat OK quality.
Note that the hardest part of all that is probably the cropping and you may be able to do that while capturing, if you’re familiar with OBS (Open Broadcaster Software). I think a lot of streamers use OBS because it is free and powerful. I use it to capture when I want to make a youtube video that has “live” picture-in-picture (like showing me driving IRL in a window on a first-person driving sim view). You MAY be able to tell OBS to just capture a part of the screen, so it is cropped as it captures. You can also tell OBS which audio sources you want to record, like the game audio and your headset mic. I don’t think OBS has editing capabilities, so you would still need to find a way to trim it to length. Maybe Windows Movie Maker could do that.
Seems like a lot of trouble for my 20 seconds silly videos, doesn’t it? LOL. But, hey, I figure now is the time to do these while it’s “just us” beta testers. But I have to figure out how to do something other than walking up/down the aisle of the cabins. 