Web Service Access key (WSAK) deprecation was announced over 2 years ago now. This has been postponed twice and will begin to get disabled in all tenants after Oct 1st, 2022.
Users may start to see notifications in Business Central if they have a WSAK enabled on their user card. This can happen whether the user is actually utilizing the WSAK or not. The notification will allow them to click into a Wizard walk-through that will remove the WSAK from their user card.
Partners can use telemetry to determine if WSAK calls are being made into the environments. Find example KQL here: BCTech/AuthenticationWithWebServiceKey.kql at master · microsoft/BCTech · GitHub