Joomla 5.2.2
PHP 8.3
Astroid 3.1.8

If I create a new section and then add a module position, no module style is set.

If I then create a new, custom module and assign it to this module position, a class for the font inserted there is automatically set and a Font AWESome 6 is used as text.

Only when I select the style none in the module position and save it, this class is removed and the system font is used. After that, you can use all styles without any problems.

Solution:
For every newly created section and the module positions it contains, the module style none or astroidxhtml must always be set.