In my case:

Caused by: org.springframework.beans.factory.BeanCreationException:
 Error creating bean with name 'flywayInitializer' defined in class path resource
 [org/springframework/boot/autoconfigure/flyway/FlywayAutoConfiguration$FlywayConfiguration.class]:
 Unsupported Database: MySQL 8.4

All I had to do is replace in build.gradle the dependencies line:

    implementation 'org.flywaydb:flyway-core'

with:

    implementation 'org.flywaydb:flyway-mysql'

Courtesy: https://documentation.red-gate.com/flyway/flyway-cli-and-api/supported-databases/mysql