Does anyone know what the actual oldest API is that's supported? This doc seems to suggest it's 2018.1, but APM flags 2019.2 as 'unsupported' in the Web Services Analysis>API Version Usage section.

FYI, we have an integration with a third party vendor that is using 2017_1 (definitely listed as unsupported). We're planning to have them move to 2022_2 with the 2023_1 Release. (Working on testing it with the vendor in RP.) We didn't get a straight answer to when unsupported becomes deprecated and no longer available.

7 years I believe for deprecated. 5 for unsupported? I had our sandbox upgraded early for testing and one of my integrations stopped working and it was due to using 2017_2. We changed everything to 2022_2 and they're fine now.