You're in luck. You don't need an extension, that's actually a new feature in Firefox.
Set up syncing. You can access that from
Edit | Preferences | Firefox Account. Pick which items, if any, you want to routinely sync between devices. Sync is the mechanism for the new feature.
Once it's set up, right-click on a tab you want to share and there is an option,
Send Tab to Device. BTW, you can also access that from the three-horizontal-dot icon on the right side of the URL entry window. You can pick any individual devices or all of them (these are the other devices on which you have also set up syncing).
The tab will show up in the Firefox session on that device (almost immediately if there is an open session, or the next time you open Firefox there).