Upgrading Spring Boot to v3.1.7 or later resolves the issue. The GraphiQL webpage displays as expected in my project.
For Spring Boot v3.1.0 to v3.1.1, the error remains the same as previously : Uncaught TypeError: e.useSyncExternalStore is not a function
For Spring Boot v3.1.2 to v3.1.6, I can build the app but cannot run it. Therefor, I cannot determine in which of these versions the graphiql problem appears. The crash on run occurs due to breaking changes and can easily be fixed by updating the related code to meet the new requirements.
For Spring Boot v3.1.7 and later, the app builds and runs as expected. However, I encounter runtime errors due to the version shift and need to investigate the update requirements for this and previous Spring Boot versions.