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I’ve had one that thought that “SSD” was a kind of RAM

Well, could it be considered random access memory? I couldn't really find a clear answer, mostly opinions.

Wikipedia says:

A random-access memory device allows data items to be read or written in almost the same amount of time irrespective of the physical location of data inside the memory, in contrast with other direct-access data storage media (such as hard disks and magnetic tape), where the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement.

So maybe?

Although that's basically the other end of "SSD is RAM".
You could also install the OS to a RAMdisk.
Gigabyte even made some physical ones in the past.

The i-RAM was a PCI card-mounted, battery-backed RAM disk that behaved and was marketed as a solid-state storage device. It was produced by Gigabyte and released in June 2005, at a time when genuine solid-state storage solutions were generally still less affordable than an i-RAM product with superficially similar capabilities. The i-RAM utilised DRAM, a type of volatile memory, and was equipped with a lithium-ion battery to provide backup power.