Haven't tried playing around with it, but there is a setting in config/asgard/core/core.php:
'admin-theme' => 'AdminLTE'
You should be able make you own fork, (or even duplicate locally) and rename it, however you wont get the updates of the original theme. Also I think some of the plugins point to the adminLte.css file directly so it will probably be a hassle. I would try on a fresh install first before messing around on a real project.
Here's how I added a custom field to the Admin Pages:
console "npm install" at the root of the project
console cd to Themes/Adminlte and "npm install"
create your db migration (I added a field to the page module) and migrate
in the partials for the Page module add your field to edit and create blades
in Modules->Page->Assets->js->components edit the 3 .vue files to add the new field
console cd to root of project "php artisan asgard:module:publish Page"
console cd to Themes/Adminlte and "npm run watch"
console cd to root of project "npm run watch"
house keeping "php artisan cache:clear" and "php artisan view:clear"
You should now see your field in the create and edit of the backend of your site. Remember to add the translation if the field is translatable.
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