I have a customized field that is called "subTitle", the date type is "String", input type is "default". If you change "default" to any WYSIWYG editor, it will be not working, it used to be working and I could edit the content through the editor. It's not working after upgrading Dnn core from 8 to 9 or 9 above Default setting for subtitle works
It shows the content of subtitle
I found the root cause. It's because in very old installations, the primary App Content
has App ID #1 which normally is reserved for system functionality.
Because of this, old input-configurations in the DB are prioritized over new ones which are in the file-system.
Just rename the input-types in the App and you should be good to go (as they are not actually used any more). I created a checklist for this: https://azing.org/2sxc/r/1yZjqy86