So far so good. As far as breaking extension go I only have issues with Dash to Dock and Blur My Shell. I can use Floating Dock until it catches up…
Evolution Mail got some flash and fancy icons for different folders:
… but several of the updates utilities don’t respect user theming like custom icons for close minimize and toggle windows - I see this on the settings and extension dialogs as well as calculator and calendar … oddly Evolution Mail and Nautilus still show the user themed icons
The legacy applications setting will only affect the ‘old apps’ that use GTK3. Newer or updated apps that use GTK4 will more or less be locked into Gnome’s choice of theme that’s been integrated into the libadwaita library.
Edit: This is my long-winded way of agreeing with @jonathon
It seems it’s certainly a lot harder to theme to the extent of previous versions but people are doing a lot with just editing the css and re-colouring all the elements at least, proper dark mode is all I’ve ever wanted.
I manually built a version of Dash to Dock to make it work. The tricky part was figuring out what current commit was a decent version working with Gnome 42. You could build your own if you want with only a few simple commands to clone the repository; and create your own branch for the specific commit and then build and install your local copy…
git clone https://github.com/micheleg/dash-to-dock.git
git checkout -b gnome42 c41fd38
by the way, there is one build dependency … you will need dart-sass (sass) or sassc … you can get more details from READ.ME in your cloned repository
Edit: downside to this approach is that you don’t get automatic updates when you build your own. I typically do this until I see a compatible version of the extension on extensions.gnome.org - then I remove my local version and install from e.g.o