[franga2000]

Not the online or browser-based signing, no, but LuckyPatcher lets you patch APKs locally (I think their specific implementation requires root, but that wouldn't be necessary if APKs were downloaded in-app). I was actually really surprised when I first found Vanced that it wasn't using something like LP and instead distributing pre-modded APKs.

[shabier]

Good call, I didn't think of that. I believe that the non-root approach for LuckyPatcher is to create a separate, (limited) modified APK file rather than modifying an existing, installed app

[roastedpeacock]

LP is exactly what I was referring to by my previous comment.