Wire can use e-mails or phone nunbers for IDs, so you can use the same ID on multiple devices. But the mobile UI is worse than Signal's and it's also it's not federated. The source for the clients is on Github. It does have desktop apps for Windiws and Mac and a web app that works in most modern browsers. It's in many ways better than Skype. You don't have to link it to your phone in order to send messages - just use an e-mail account. It's also run by a Swiss company, so the servers might just be outside of the US.