I found in my history the following command:
sudo keytool -import -alias myssl -file /usr/local/share/ca-certificates/extra/nas.crt -keystore /opt/jdk/zulu11.48.21-ca-jdk11.0.11-linux_aarch64/lib/security/cacerts
I’m quite confident that this did the trick.
nas.crt is the certificate exported from the NAS-drive