In December 2018, Beck posted a 40-second clip on Instagram of him sitting in a yard by a tree, playing acoustic guitar. He captioned it "serenading the sirens," because as he played, police sirens can be heard in the distance.
You can watch it until he deletes it:
I do not know if it's an actual song, a cover, complete, or just some freestyling acoustic improv in the moment.
If it is an original thing, it will probably end up on an album in like 2030 though.