With the recent update to the EE4J Parent Pom 1.0.7, Kevin Sutter decided to initiate the processing for Jakarta EE 9.1 and generated the first RC for the APIs.
Per the 9.1 Release Plan, there are no updates to the Jakarta EE component APIs in 9.1. Jakarta EE 9.1 is strictly in support of the Java SE 11 runtime. Thus, these API jar files are a convenience to correspond to the eventual 9.1 Specification update.
https://search.maven.org/artifact/jakarta.platform/jakarta.jakartaee-api/9.1.0-RC1/jar
https://search.maven.org/artifact/jakarta.platform/jakarta.jakartaee-web-api/9.1.0-RC1/jar