Thank you for sharing an exact command which works. I’d tried some similar commands myself but they did not work. Do you know what the exact requirements are to invoke a new profile?
Whatever is in your command definitely has the magic as I was able not to just add the Samyang profile to a file without EXIF lens info but replace the info from a zoom (old file with Sigma 150-600mm f5.6-6.3: terrible lens, returned it for the more expensive but very good Canon 100-400mm IS L II). New profile recognised in both FastRawViewer and PhotoLab 2.
As some have mentioned, it’s necessary to move the image to a new folder. Creating a new project is not enough. The image must be physically moved or the folder renamed (haven’t tested renaming folder actually, only physically moving the image and creating a new project. It’s pretty crazy that a new project isn’t enough.
There’s a workaround to delete the whole database. On Mac the database hides here: /Users/~/Library/DxO PhotoLab v2/DOPDatabaseV2.dopdata
As I don’t want to move my images around all the time, I guess I’ll be using that workaround regularly. Rescanning images/folders would be a very welcome addition to the File menu.