Lots of aqara stuff on sale at Amazon. Some at 10% off, most at 15% off, some with even higher discounts.
I use mine (The Zigbee ones, anyway) connected to an Aqara hub that acts as a “matter bridge“ and then bring them over to SmartThings that way. It doesn’t work for all features or all models, but it works for a lot, and the connection will be local with no custom code required.
The button is on a particularly good sale, 40% off, so $15. I use one via matter over bridge and it works well.
You can also connect many of the Zigbee ones directly to SmartThings, although you might need custom edge drivers. It just varies.
At the time of this posting, the Wi-Fi ones are not compatible directly with SmartThings.
The following page lists the models that can currently be bridged via matter:
Unfortunately, the new M3 hub is not included in the sale. But if you just need a basic matter bridge for aqara, the E1 is under $30 and has a 5% discount.