Any version other than 2.7.6 and 3.0.0 (or higher) should be ignored. Everything before version 2.7 is already end-of-life unless you have paid support.
You can upgrade to Spring Boot 3.0.0, but that's going to be a pretty big step from 2.3.x. The two biggest changes:
It requires Java 17 or higher (yes, really!)It switches from Jakarta EE 8 (javax package prefixes) to Jakarta EE 9 (jakarta package prefixes)
If I were you, I'd upgrade to Spring Boot 2.7.6 now (and then keep updating to latest patch versions). A lot will still work; I have created a Spring Boot starter that I haven't had to change since Spring Boot 2.2.x. There may be some issues though, but these can mostly be solved by reading the release nodes:
2.42.52.62.7
Once you're using Spring Boot 2.7, you can start migrating to migrate to Spring Boot 3.x; version 2.7 isn't going to be end-of-life until next year November. Fortunately, there's a migration guide:
https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.0-Migration-Guide.