I will be doing 100% streaming. I’m not going to be ripping any music at all so is there any need to purchase an SSD for a K21?
Short answer is NO.
However, adding an SSD does enable saving Roon Back-ups on the server, and having a small local library.
If you have no SSD do not back up Roon to the Antipodes, as it will fill the OS SSD rendering it inoperable.