Nextcloud 20 allow upload but not delete

I’m currently on NC 20 and have an “external storage” mounted where I keep my data. How can I allow users to upload, but not delete files? It used to be the file access control app could do that, but now with the “flow” based way of doing it, I don’t see how I can do that. How can I allow my family to upload to the directory, but not be able to delete from it?

Send them a share link url as upload-only for sending files.
Share the destination folder as read-only with your users.