Not recommended as less reliable than HDDs

This is possible, e.g. ORICO makes installation adapters for this purpose... but I would not recommend it for this purpose in a NAS, because in contrast to HDDs, the write cycles per data bit are limited in an SSD.... and, admittedly, expire after many cycles. Mine has been in continuous operation with original HDD disks for NAS for more than 6 years. I have spare hard disks and a second NAS in stock - the NAS itself can also fail.... and then? Where to put the disks?
So full redundancy