Dell monitor without speakers -- best way to connect speakers

@TGNYC14  Dell makes some soundbars that are designed to attach to the underside of display panels or the vertical portion of the stands, but none appear to be compatible with the S2719D, possibly because it's specifically designed to be ultra-slim unlike its business-oriented P and U Series displays.  Dell's only recommended audio accessory on the S2719D's page is the AE415, which is a pair of small freestanding speakers.

So it appears that the display has no bearing on the audio solution you choose.  You've got options ranging from Bluetooth speakers/soundbars, basic USB-powered speakers, externally powered speakers that receive the actual audio signal via USB or a 3.5mm round headphone jack, and even connecting to an AV receiver.  For reference, Bluetooth can come with a quality compromise due to its limited bandwidth for audio, and it can also have a bit of latency, so if you plan to use it for watching videos rather than listening to music, you might notice that the audio and video are slightly out of sync.  On the other hand, there are several Bluetooth speakers that include built-in batteries and are therefore portable, so if you think it might be nice to have something that you can use with your Mac at your desk where it would be connected to wall power, but still take it with you if you ever want to have music outdoors somewhere, that option might be worth considering.  And in fact some portable Bluetooth speakers also support receiving audio via USB or 3.5mm jack, in which case you could even avoid the Bluetooth audio lag issue when using it with your Mac, while still preserving that portability option.

So as with many things in life, it really depends on what you want in terms of quality, physical size, flexibility, and of course cost.  But you can run just about any speakers from your Mac.  It's just a question of possibly needing a suitable adapter, but that depends on what speaker set you choose and the specific MacBook Air you have.  Apple has made a few generations over the years, and even multiple sizes, and they don't all have the same ports, so it's helpful to specify the exact size and generation of a product you have.