Encountered the same issue with a Dropbox link. The message looks like this (identifying details redacted):

  "content": {
    "msgtype": "m.text",
    "body": "www.dropbox.com/scl/fi/xxxxx...",
    "m.mentions": {}
  },

there doesn’t appear to be anything on Matrix’s side that acknowledges the full link text

peering into what the bsky web app shows, I see this:

            "lastMessage": {
                "$type": "chat.bsky.convo.defs#messageView",
                "id": "xxxxxxxxxxxxx",
                "rev": "xxxxxxxxxxxxx",
                "sender": {
                    "did": "did:plc:xxxxxxxxxxxxxxxxxxxxxxxx"
                },
                "text": "www.dropbox.com/scl/fi/xxxxx...",
                "facets": [
                    {
                        "index": {
                            "byteEnd": 31,
                            "byteStart": 0
                        },
                        "features": [
                            {
                                "uri": "https://www.dropbox.com/scl/fi/xxxxxxxxxxxxxxxxxxxxx/xxxxxxxxxxxxxxx.jpg?rlkey=xxxxxxxxxxxxxxxxxxxxxxxxx&dl=0",
                                "$type": "app.bsky.richtext.facet#link"
                            }
                        ]
                    }
                ],
                "sentAt": "2025-03-17T23:41:00.403Z"
            },

so in theory at least it should be possible to either replace the truncated link with the full uri, or create a rich text link out of it

hope the added context helps!