Can i use gnome and sway both on EOS?

Is it advisable to use both the GNOME and sway desktop environments simultaneously? Could this potentially make EOS unstable?

You can technically run it alongside a DE, but you may have to edit some configuration files. I found the best way to run Sway was without a login/display manager (starting it from TTY), and if I wanted to switch to a desktop I used (as an example) systemctl start lightdm.service and logged into it from there.

I can’t confirm if that’s the best way to do so from Gnome/GDM, but it’s possible. Just keep in mind you’re going to have both environment’s applications visible to the other.

will GDM detect sway session on login manager ?

The Arch Wiki says that it will be detected, yeah. https://wiki.archlinux.org/title/Sway

It’s also noted that login managers aren’t technically supported