Metis theme is now running on bootstrap5
The ways how to customize admin area (That ones I found)
The site was updated to 2.3.1 stable version
Using WP for areas when e107 fails and e107 for adminstration custom things
Navigation menu was added some time ago to core
There was significant change in core during 2-3 days ago, so don't sync with git until you check your theme. Maybe older php version are safe, I don't have time to dig in core to find it. That change is improvement...
Support this theme now with a donation of 10€ and you will get access to its tutorial and anything related to this theme. This price shall apply until I add the first premium plugin.