Old Reddit on desktop, but that's usually for modding or typing up longer posts. Just browsing I normally do on mobile, through Boost. If I have to mod on mobile, then it's a combination of Slide and RIF.
There's a nice post about it on the superuser forum here (along with more in-depth posts that you can easily find by searching).
PF = Port Forwarding
w/ = With
wo/ = Without
The TL;DR is that at least one person must have PF enabled in whatever operation you're performing. So if you're downloading wo/ PF enabled, then you can only download from seeders w/ PF enabled. If you're seeding wo/ PF enabled, you can only seed to downloaders/peers w/ PF enabled.
You'll notice that if you have PF enabled, you're guaranteed to have all options open, whereas if you don't, you're more limited (although in most cases are still able to perform P2P normally)
Do you use reddit mostly through the app or web?
Because I only use web, on mobile and desktop. I can't live without adblock.
Removing the support for forwarded ports - Blog | Mullvad VPN (mullvad.net)
Mullvad will removed port forwarding from their app.