there is no "unknown sources" apps option in my apps view

That page is for enabling PCVR unknown sources.

Unknown sources category won't appear in your headset unless you actually have some apps from unknown sources installed first. There's no toggle for the headset, you just have to enable Developer Mode, install SideQuest and some of the third-party apps. Unknown Sources will be buried in one of the menu lists on the left side of Navigator.

I do have some 3rd party apps installed. I was able to see them before the big update and I have to manually launch them by sidequest now.

 The issue is that there is no such option. Just All, Horizon+, and download, 3 options.