For those looking how to do this in 2024, with java 17+ modules, etc. A very easy way is Keytool explorer

With that, you don't need any weird setup as it supports BKS (and BCKFS).

Simply open the keystore which you want to convert, open the keys by entering the appropriate passwords, and then File->New keystore, select BKS, and drag the keys/certs to the new keystore. Save it, enter the new password, and done.