Start from here https://wiki.debian.org/DebianRepository/Setup

KDE Neon is based on Ubuntu LTS, you’re fine.

Stick with what you’re familiar. You can run Proton with any distro most likely.

Yeah, that’s what I’m using.

That’s what I’m using now :)

Really? Apollo was the best client, kinda miss it and the reddit that used to be.

Digg is still alive?

There was a time when you had to pay for the next major version. I think it went free around mountain lion or so?