I made it working:
1. Clone the Signal-Desktop Repo
2. Edit the File: &quot;js&#x2F;background.js&quot; Line 56 SERVER_URL to &#x27;<a href="https:&#x2F;&#x2F;textsecure-service.whispersystems.org&#x27;" rel="nofollow">https:&#x2F;&#x2F;textsecure-service.whispersystems.org&#x27;</a> and Line 57 ATTACHMENT_SERVER_URL to &#x27;<a href="https:&#x2F;&#x2F;whispersystems-textsecure-attachments.s3.amazonaws.com&#x27;" rel="nofollow">https:&#x2F;&#x2F;whispersystems-textsecure-attachments.s3.amazonaws.c...</a> and save it
3. Open chrome:&#x2F;&#x2F;extensions&#x2F;
4. Activate Developer mode
5. Click &quot;Load unpacked extension...&quot; and select the Signal-Desktop directory
6. Open <a href="https:&#x2F;&#x2F;textsecure-service.whispersystems.org&#x2F;" rel="nofollow">https:&#x2F;&#x2F;textsecure-service.whispersystems.org&#x2F;</a> and accept the cert (otherwise you won&#x27;t see the qr code)
7. Scan the qr code and have fun!