"the way folders are managed seems to have changed"
You have encountered the new Android file model called "scoped storage". This model arrived along with Android/11+, and specifies exactly which app-private folders may be used for chart storage
. Previously accessible public folders (e.g. the root of an SDCard) can no longer be directly accessed. Contents must be migrated to a permitted private folder. It can be disturbing at first, but long-term provides improved app storage
management and security
You can read more about it at the OpenCPN for Android Forum.