Didn't have time yet to watch all of the video, but on my own GrapheneOS device, and assume especially useful on tablets, I have been using Molly for Signal messaging.
Its cool because I can use an existing account (already attached to a phone number) so the device doesn't require a SIM. The normal Signal app does not support this.
Unfortunately at the moment I am having to use "Molly" not "Molly FOSS", meaning I have some of the proprietary blobs in normal Signal app. It is currently too much hassle (for me) to setup notifications with the FOSS version.
Wikipedia says Gen Z is born from mid to late 90s, which makes me a Gen Z'er. I use adblocker and try combat enshittification a few ways, including contributing to the commons. My day job is being a firmware developer for an opensource company. I'd say I'm tech savvy.
I think there are quite a lot of people like me, it is just that there are more people using technology at younger ages, effectively diluting the pool of Gen Z'ers you are encountering both online and in person.