やっぱり Cloud Console からは Google Cloud Functions に JAR ファイルをデプロイできなさそうに見えるエラーメッセージ。
Build failed: function has neither pom.xml nor already-built jar file; directory has these entries: .googlebuild, META-INF, ch, com, functions, info, org, [t]2021-10-22 13:54:02
ERROR: (gcloud.functions.deploy) OperationError: code=3, message=Build failed: function has neither pom.xml nor already-built jar file [t]2021-10-22 14:52:44