Got a PinePhone Pro with 4GB.

> I suppose it's limited to very few tabs

Not really. Haven't used it super heavily, but I haven't felt limited by tabs. It can handle multiple YouTube tabs, too.

> Some very lightweight DE could likely make it more usable. Running something like WezTerm + tmux as the DE

I use sway on it. It's perfectly responsive. I expect i3 with Xorg would also be. Neither count as a DE, but neither does a terminal + tmux.