Not to have just read & think you saw it all; then may have failed to see clearly, with depth.
First thing with older intel-based hardware and the limits therein, some of those do have
a hardware upgrade path. Others are inert, totally sealed against new hardware upgrade.
Newer integrated S.O.C. Apple Silicon is very sealed; later models offer better options.
The model year has set limits; was previously generally described; your next step will be
buy new build model year computer. Additional years of usefulness have been expended.
..Second owners of such a model, won't get much use from limits now set by last upgrade.
To see what may be available to upgrade the hardware, OWC has a webpage to find IF the
newer replacement parts are available for your MacBook Air. [Between certain years, only.]
But the idea is to get the most for your money, unless you prefer to sell or throw away $$.
hidden limits https://eshop.macsales.com/upgrades/macbook-air-13-inch-mid-2019-1.6-ghz
https://eshop.macsales.com/upgrades/macbook-air-13-inch-mid-2019-1.6-ghz/external-storage
An external bootable storage drive could work, & have workable space macOS. Since yours won't
support an internal larger capacity SSD. https://eshop.macsales.com/item/OWC/TB3ENVPFX02/
The Envoy Pro shown, has 2TB capacity & runs much quicker than stock; figure for other specs.
..Other various external storage including large bulky or optical drives are in main search above..
I've trimmed my older Macs to only three that I use, along with some older image editing software
limited to those model years; two of those are still plodding along nicely. The G4 late 2005 Mini 1.5
runs Leopard 10.5.8, and has good options there, for use with older Nikon D70s & Lumix DMC-FZ1.
(Later ones are Mid 2012 MacBook Pro 13-in; and Late 2012 Mac Mini quad-core server 2.3 with 2
drives, each with two physical partitions on both; & four macOS installed. Newest, Mojave 10.14.6.)
Nicer external drives are helpful when they can run clones, for complete startup/backups.
Consider altogether the total count of rescued older Macs that were donated to charity
amount to 600 complete machines with software, displays, & printers. In mostly rural AK.
I've lived here awhile, and found a few hobbies; and avocations. I also collect & use film
cameras with several lenses; not sure last count, numbers now stored, vs. those in use.
Also I prefer the outdoors, remote work can be a joy; even sub-zero w/ limited daylight.
With climate change very real here, can't hardly carry enough layers, to gear up or down.
Take care & safe travels!
⛵️🎣🏕|🐶😻|❄️🌞|🍏🍄