The developer of mabox is doing a great job and is indeed using Manjaro as the foundation.
mabox is providing a great UI for a keyboard oriented user.
I do think that you should try asking in the mabox linux forum as I am confident they know a lot more about the inner workings and how to solve issues for your system.
system maintenance
I am a huge fan of proper system maintenance because
- The system does not maintain itself.
- Obsolete packages does not remove themselves.
- The package cache does not empty itself.
- The kernel should not change major version itself.
- Yet the kernel does change itself if it marked EOL (linux-meta magically appear)
- The kernel packages continues to build up
Some ideas on how to keep your system in shape
packages
If the Manjaro Package Manager pamac is installed on your system - you can set the number of packages to keep in the applications Preferences.
You can also use the Installed tab to find all installed packages, remove applications you don’t actually use. Especially note the Orphans and Foreign in the left pane of the Installed tab
All packages on your system contribute to the size of any update.
Always recheck your Orphans after removing an application, keep clicking remove all until the list is empty.
kernels
As you already know kernels older than 6.6 has issues with polkit.
You can use the Manjaro Settings Manager to weed out in your installed kernels.
My personal unofficial recommendation is to use the latest LTS kernel, which - as of 2026-07-06T22:00:00Z is Linux 6.18.
My personal experience is, it is rarely the kernel that prevents a system from launching the GUI, in most cases it is caused by the GPU driver, predominantly Nvidia.