[Testing Update] 2022-06-03 - Linux 5.18, Systemd 251, GNOME 42.2, NVIDIA, Mesa, Pulseaudio, Perl

Sure it does. Use a compatible theme like Adw-dark. Also install the Legacy (GTK3) Theme Scheme Auto Switcher (gnome-shell-extension-legacy-theme-auto-switcher) GNOME Shell Extension and both Libadwaita and legacy applications will automatically switch themes.

That is neither necessary nor supported.