UniClip is described as 'cross-device clipboard synchronization tool'. There are seven alternatives to UniClip for Mac, iPhone and iPad. The best alternative is Paste. It's not free, so if you're looking for a free alternative, you could try CopyClip or Pasteboard Viewer. Other great apps like UniClip are Copied (Paid), PastePal (Paid), iClip (Paid) and SmartPaste (Freemium).
CopyClip 2 is the slickest and most efficient premium clipboard manager for your Mac. Running discreetly from your menu bar, the app stores all that you have copied or cut in the past, allowing you to quickly find that snippet of text you've been looking for.
PastePal is a native macOS application that allows us to easily manage pasteboard history, notes and shortcut. The app displays nicely in light and dark mode, and visually accessible via side bar. You can toggle side bar via shortcut Cmd Option Alt P.
Copy-paste nicely styled text to apps like GMail and Google Docs without learning new shortcuts. Every time you copy styled text, say from the web, SmartPaste automatically cleans out all unwanted styles, while keeping the useful ones.