Have you tried the Emoji add-on for Firefox? It's developed by me, Sav!
With "Emoji" add-on you can find any emojis easily and copy them, just with a click. You can also use the search-box to find a specific emoji or you can use the Most used emojis section to find emojis you use frequently.
You can customise completely the UI: for example you can change the theme (light or dark), you can change the icon size and the rows and columns number.
The add-on supports 1702 emojis (UNICODE 12) divided in 13 sections (plus most used emojis and the search section): Smileys, People, Animals, Symbols, Foods and drinks, Flags, Sports and everything related to them, Travel and places, Technologies and office, Clothes and accessories, Hands and parts of body and Other.

The add-on is free and open-source and you can find the source on GitHub.
You can buy me a coffe on PayPal, Ko-fi and now directly on GitHub as well.
You can also review the add-on, it's free and it doesn't require too much time.

Now, 26th July 2020, 254 users use the add-on and they continue to grow... so, really thank you!

Link utili
Download the add-on on Firefox Add-ons (AMO)
Buy me a coffe on PayPal
Buy me a coffee on Ko-fi
Emoji on GitHub