Can't invite users from federated homeservers with allow_profile_lookup_over_federation: false

[rfalkenstein]

Description

Currently, it's not possible to invite users of a homeserver which has "allow_profile_lookup_over_federation: false" . The element client throws "unkown server error".

Steps to reproduce

• Have two federated homeservers A and B
• Homeserver B has "allow_profile_lookup_over_federation: false" set
• A user from Homeserver A tries to invite a user from homeserver B on a current Element version (in my case 1.11.99) to a room (direct communication, however, works)
• User A (of Homeserver A) receives the message "Unknown server error" and can't invite User B (of Homeserver B)

Homeserver

any homeserver using allow_profile_lookup_over_federation: false

Synapse Version

129

Installation Method

Debian packages from packages.matrix.org

Database

single

Workers

Single process

Platform

vm

Configuration

allow_profile_lookup_over_federation: false

Relevant log output

Please check the log from: 
https://github.com/element-hq/synapse/issues/18280#issuecomment-2827961845

Anything else that would be useful to know?

This is the same bug report as https://github.com/element-hq/synapse/issues/18280 and https://github.com/element-hq/element-web/issues/29028. I think, however, it would help to have a fully filed bug report in the correct repository. Please close if it doesn't.