In addition to what @ad_sahota:
Spring Boot 3.2 will be part of Camunda 7.21, scheduled for April 9th 2024 and you can already test it with Camunda 7.21.0-alpha3 release.
If you check the latest version of the documentation you can see that the compatibility matrix is already update:
In addition, please check also: Camunda Automation Platform 7.21.0-alpha3 released