You can reset the SSD's internal encryption key via hdparm, too, once you're done "deleting" luks header. It takes somewhat longer time, but if the SSD firmware

You can reset the SSD's internal encryption key via hdparm, too, once you're done "deleting" luks header. It takes somewhat longer time, but if the SSD firmware is not completely stupid, it will be the equivalent of deleting the LUKS header and running TRIM on the whole device afterwards.