The Switchbot hub is a an IR blaster, so you can actually do more than just on/off by setting up scenes in Switchbot (not ST scenes), but it’s clunky and limited.
A lot of people use Broadlink which works pretty well and is also inexpensive but there’s no official integration and setting it up can be a little technical.
Alternatively, open the SmartThings app and look at the options under air conditioners. A few of those may be full air conditioners but most will be IR blasters that look like a thermostat to ST. These will likely cost more than Broadlink but will probably be easier to set up with full thermostat controls. Cielo Breeze is a popular model.
The following is a good recent discussion:
Seeking advice on automating mini-splits (2021)
That said, IR only sends one way commands to the air conditioner, it doesn’t get status updates from it. So if someone sets the controls manually or uses the ac’s own remote, ST and the IR blaster won’t know about it. That’s true regardless of what IR device you choose.