Firefox has a nice feature that lets you log in to a Mozilla account. If you log in to the same account on multiple computers (or phones), you can send tabs between them.
I use this feature to send ephemeral text using https://temporarynote.com. temporarynote lets you put arbitrary text in a URL. Check out this example.
Using this method, I can share text between two computers using just Firefox. Today I used it when I was setting up Syncthing on my laptop. When I was setting up folder sharing, I needed to copy the device ID from my desktop PC to my laptop. This temporarynote trick was a good fit.