PS: if you maintain your own software and aren't able to find a way for your user to do shares - especially while systems that most likely have such functionality built-in out of the box surely exist, think Nextcloud etc - that is covered by how Linux is supposed to be used, by definition it's pretty much out of support. Especially if you keep insisting on using a way that was never officially supported, just because you got away with it for 15 years.