Yeah I've just tried Theia. Vscodium is still the way to go. I just wish they had answers for issues like running extensions that depend on cpptools. I managed to work around it by installing an old version of cpptools from before the nag prompt that checks you're running it in vscode was added.

Zed is almost a good solution but like most they are missing most of vscodes markdown editing features*. Also, right now there's no way to hide the sign in and ai buttons from the UI.

* https://code.visualstudio.com/Docs/languages/markdown