CKEditor 5 only works with HTML-based text formats. The "Inline SMS" (filter_inline_sms) filter implies this text format is not HTML anymore.

This submodule will not exist in future versions, 🌱 [policy] Announcing closure of 3.x issues if they are not applicable for V4 Active .

I still need to use smsframework 2.3. I understand that this submodule is going away and that is why you do not want to fix it.

But for those of us still on 2.3 let's see if we can fix it

With selecting "Inline SMS" these additional errors occur that cause ckeditor5 not to be installed:

Error message
'display' is not a supported key.
'display_text' is not a supported key.
'default_icon' is not a supported key.
'custom_icon_path' is not a supported key.