But this does not fix the issue that headers having a .hpp suffix are still not found.

I use nowadays a data asset. To create a data asset add a "New data set" to (one of) your xcassets files, give it a name and add the data. In your app you can access the data by using the NSDataAsset class. PS: This may not be a good solution for large data sets.

Unfortunately, each version of Xcode introduces a new bug into autocompletion of headers. So, this keeps you busy filing a new bug report whenever a new version is released. Xcode 14 solved an autocompletion bug of the previous version (additional " or > characters were added to the include path), now, autocompletion does not work at all anymore for user defined include paths. For system include paths it works in the sense that the closing > character is not added anymore.