This week was a bit of a slog with the same PR (https://github.com/mne-tools/mne-python/pull/10913) as before, and although it's not the central focus of the project, I think it will greatly improve the maintainability and long-term adoption of this project within MNE because the backend is such a fundamental thing to all GUIs. I hope it might even be used outside of MNE, as I think it was a really worthwhile framework. This week will proceed onto the time-frequency source estimate aspects without any further ado. What ended up taking a long time was versioning issues with the dependencies and tweaks to make both the notebook and pyvistaqt backends look as similar as possible. Also, a lot of the functionality for notebook had not been implemented yet. Finally, it also took some time to implement the backend (partially) for mne.viz.Brain to troubleshoot parts that didn't work and show that it could be the framework for a GUI. This week, I am moving on to the new source space class definition which hopefully I will be able to finish tomorrow although I am on vacation Wednesday-Friday.