I installed Sway onto my PPPro and the first time it booted after installing was fine. Everything worked as I expected. I followed the initial popup which updated my sources and checked for updates but there were none.
I turned the laptop off and the next time I turned it on, after login sway only shows a blank screen.
I can still access the shell via starting a new tty with `CTRL-ALT-F*".
My display manager is sddm.
If I try to manually run sway, I get the same result. Blank screen.
I can tell other things are loading, like pulseaudio. The PPPro makes a popping sound, which is normal.
SDDM commonly causes issues with Sway because it still runs on X11 only. I think there are plans to address this in some way on the next release, but until then I would suggest using something else.
A popular login manager for Sway is greetd, or as Pudge mentioned you can just launch it from the TTY.
You may have a better experience with i3, due to package availability being more modest on ARM than x86. My guess is more Xorg packages have been ported to ARM than Wayland packages.
I might give that a try, that is the login manager that Manjaro uses and Manjaro with sway boots fine everytime. I have some other personal issues with Manjaro, so I would prefer an alternative like EndeavourOS