OFTC bridge: Failed to make link: Malformed Scalar response

[Linkid]

Describe the bug When I try to bridge the #fofix:matrix.org matrix room with the #fofix OFTC channel via Elements, I get the following error message: "Failed to make link: Malformed Scalar response". In the browser console, I have the following request / response:

POST https://scalar.vector.im/api/bridges/irc/_matrix/provision/link
{
    "matrix_room_id":"xxx",
    "remote_room_channel":"#fofix",
    "remote_room_server":"irc.oftc.net",
    "op_nick":"Linkid",
    "key":""
}

HTTP/3 500 Internal Server Error
{"errcode":"M_UNKNOWN","error":"Failed to make bridge request"}

On the Matrix side, I am admin of the room. On the IRC side, I am a chanop of the #fofix channel. I see the MatrixBridge user joining and quitting the channel, but I have no private message from it to confirm the bridging.

To Reproduce Steps to reproduce the behavior:

1. Go to #fofix:matrix.org matrix room
2. Click on "Add widgets, bridges, bots"
3. Click on "IRC" in the "Bridges" section
4. Fill the form (see the screenshot)
5. Request integration
6. See the error message

Screenshots

[apos0]

Issue still persists. Can't bridge to OFTC

[bnjbvr]

Fwiw, I'm getting the same error when trying to bridge a room of my self-hosted synapse server with libera.chat.

[LuccoJ]

I also encountered this on Libera.chat while helping someone set up their bridged room.