Some extensions in devcontainer are not installing correctly. For example pylance, my current solution is to manually install it and reload the window.
I do have similar problems, some extensions are not installed even if they are listed in devcontainer.json. They can be manually installed but by default they are not there.
The problem seems to be only in Cursor, VSCode installs them all automatically
Same problem here. yy0931.vscode-sqlite3-editor is listed in the devcontainer file but I still have to install it manually. VSCode still installs it without issue
Improvements coming to dev containers hopefully, which may fix some bugs and improve stability. Keep an eye out for an update in the near future on this.