Buzz Droids appear early in Revenge of the Sith during the Battle of Coruscant. They are a weapon of the Separatist Army that are pretty cool in design and just the entire concept of them is kind of genius.
They are basically little parasitic like droids that instead of having weapons on them, they land on enemy ships and slowly pick them apart.
A swarm of these little droids descended on Obi-Wan’s starfighter and if it wasn’t for Anakin, they would’ve been the death of arguably the greatest Jedi in history.
Buzz Droids could easily be worked into the storyline of The Rise of Skywalker. The Resistance has been scouring the galaxy for any weapons it can add for its fledgling army. If they came across a battalion or two of Buzz Droids they could come in very useful. The First Order clearly has what looks like an endless fleet of Star Destroyers in the trailers for Episode IX.
If the Resistance deployed a couple hundred of swarms of Buzz Droids at them, they could take out a few of those big Star Destroyers in a matter of minutes.