Make the second hard drive non-ejectable

Hello all,

I was very excited to receive my Librem13 as I am switching over from Mac.
The configuration I bought had both the default SSD and a 250GB M2.

As I had a spare 1TB SSD from another (windows) laptop, I switched out the original SSD with that one and kept the M2 in place (as easy as advertised). The OS is on the M2 so it worked like a charm.

I formated the disk to ext4 filesystem in the hope it would recognize it as a native part of the system. However it now pops up as an ejectable hard drive unlike how it was behaving with the original SSD.

Here is my question: how do I get the SSD to be recognized as before and not just as a storage device?
How can I seamlessly make the system work between both drives (for example using by default the larger drive to stores files in my personal space instead of reverting to the M2).

Thank you for your help!