Allow approval from other instances' users (Federation)

[Extarys]

How to use GitHub

• Please use the 👍 reaction to show that you are interested into the same feature.
• Please don't comment if you have no relevant information to add. It's just extra noise for everyone subscribed to this issue.
• Subscribe to receive notifications on status change and new comments.

---

Feature request

Which Nextcloud Version are you currently using: (see administration page)
Nextcloud Hub 9 (30.0.4)

Is your feature request related to a problem? Please describe.

I have a main nextcloud instance and a secondary instance.
I need to ask for approval from a user or group of users on the secondary instance, but typing user@instanceB.local doesn't show the user.

Describe the solution you'd like
Add better federation support

Describe alternatives you've considered
Send the confidential files by email 😆

Additional context