AirDrop is quite convenient to send files to a colleague or another device without having to send an email or uploading it somewhere. At some point (I forgot with which exact OSX version), AirDrop was updated and required Bluetooth. Since then, it often occurs that the device I want to share a file with does not appear. However, there is this option to “Search for older Macs”. In the past, I’ve only used it to send files to a Mac running an older OSX version.
However, as it turns out, even for newer macOS versions, if this is done on both devices, it works much better and the device appears almost immediately.