To reset the password of an admin with the email admin@domain.com, open a Web terminal:

export MB_DB_TYPE="postgres"
export MB_DB_HOST=${CLOUDRON_POSTGRESQL_HOST}
export MB_DB_PORT=${CLOUDRON_POSTGRESQL_PORT}
export MB_DB_USER=${CLOUDRON_POSTGRESQL_USERNAME}
export MB_DB_PASS=${CLOUDRON_POSTGRESQL_PASSWORD}
export MB_DB_DBNAME=${CLOUDRON_POSTGRESQL_DATABASE}
source /app/data/env.sh
java -jar metabase.jar reset-password admin@domain.com

This will produce an output that contains the token: (example)
...
OK [[[1_63d77453-846f-44ca-939e-7aa0fa09b870]]]

Navigate to https://metabase.example.com/auth/reset_password/1_63d77453-846f-44ca-939e-7aa0fa09b870 to reset the password. Be sure to replace the Metabase domain name and the token with your own.