I also was interested in knowing how mainline support for the 3588 in kernel 6.8+ affects these boards - I'd love to be able to install debian with a mainline kernel on my CM3588 NAS board...

I put a second NVMe onto my CM3588 NAS board to test this and both were recognized without an issue, so I suspect you're correct and it's related to the NVMe modules you're using.