Hi @Korin36
If you are only listing on the Airbnb platform, they are offering a new smart lock integration within the Airbnb App. Hosts in the U.S. and Canada have access to this feature (looks like all your properties are in the U.S. If you opted in early, supposedly you should have access to it now. If not, the new release should go platform wide in a few days (Jan 26th, 2023). Right now it looks like Schlage locks are eligible now and Yale & August should be soon. I would just wait a few days and see if you like the Airbnb free smart lock integration.
If you plan on listing on other platforms, you can use the 3rd party software programs you referred to. I hear RemoteLock mentioned quite often by US Hosts (I have not used them). There are others out there, so maybe some Hosts who use those paid, 3rd party software vendors can comment here. Below is the Airbnb Help Article about their new smart lock integration:
Connect A Smart Lock to Airbnb
https://www.airbnb.com/help/article/3478