I cannot share a tab from my phone to my tablet or vice versa. I can send tabs to my desktop computers, and my desktop computers can send tabs to my phone, but for some reason Firefox Sync thinks that my phone and my tablet are the same device.

Curiously, when I go into my Firefox account settings and change the name of my browser on each device, as soon as I sync, the names are swapped. Specifically, I named Firefox on my phone "S23 Ultra". When I checked the settings on my tablet, it showed that that was also the name of Firefox there, too. So I changed the name of it on my tablet to "Tab S8+". As soon as I hit "Sync Now," my phone changed to "Tab S8+". And when I changed my phone back to "S23 Ultra," as soon as I synced my tablet, that became the name of my tablet browser, too.