[ydant]

If you're using AWS ElasticBeanstalk Tomcat distribution, 21 isn't supported yet. I realize this isn't a huge segment of the market, but it's probably not the only example.

https://docs.aws.amazon.com/elasticbeanstalk/latest/platform...

21 is supported for Amazon Linux 2023 and the JavaSE ElasticBeanstalk offering, though.