In this world of after 3.5 mm, Bluetooth is the most universal option. But many older electronics still do not support wireless audio. Cub, now there's a dongle for that.
The AirFly dongle (from $ 34.99 on Amazon) can be connected to any 3.5 mm headphone jack (mini-jack) and offers a battery-powered Bluetooth receiver for that audio output source. So it's not something that you would connect behind the TV or leave somewhere in the long run, but if you are in a place with an aux port and you only have a few AirPods, you want this in your laptop bag.
Simply charge the dongle with the included micro-USB cable and then connect the supplied two-head headphone cable. One end goes into the dongle and the other end into the 3.5 mm line-out port.
Put the dongle into pairing mode if this is the first time you use it with your headphones and do the same for your headphones themselves. AirFly then automatically connects to the headset as soon as it is seen in pairing mode.
But know this in advance: the classic AirFly dongle is a Bluetooth transmitter not a receiver or a transceiver. This means that it only works with audio connections that output audio and the connection goes only one way: from the output source to your Bluetooth headphones.
For example, you cannot pair your phone with AirFly to convert a speaker with an aux connection into a Bluetooth speaker. If you want something like that, you're better off with the AirFly Pro ( $ 54.99 on Amazon). It is a transceiver, so it can provide a Bluetooth connection that works as input or output.
Even the cheapest options from AirFly come with high-quality audio codecs such as aptX, Bluetooth 4.1+ support and a battery life of 8 hours. So unless you are on an intercontinental flight, it goes all the way and you have a clear, clear sound.