> The only way I could get data off their proprietary SHR system (which is great, except when the HW breaks) would've been to buy a new Synology system, put the drives there and pray it works out of the box.

First,

https://kb.synology.com/en-global/DSM/tutorial/How_can_I_rec...

It's just mdadm and lvm.

Second, putting drives in a new NAS isn't hoping it works. It's an official and supported upgrade path,

https://kb.synology.com/en-global/DSM/tutorial/How_to_migrat...

In case it helps in the future.