We strongly discourage using an MBR (Master Boot Record) storage device to install Nitrux because the MBR partition table supports only four primary partitions, and Calamares can’t continue the installation. We strongly suggest using a different storage device for the Nitrux installation that does not use MBR, deleting the partition table, and using GPT (GUID Partition Table) instead. Alternatively, visit this AskUbuntu link to learn how to convert the partition table from MBR to GPT without data loss. This problem is neither a Nitrux bug nor a Calamares bug.
Also, be aware that deleting the partition table will delete the data on the storage device.