But here, DSM and DDSM are on the same DS (the 216+II).
From Synology perspective those are not the same architectures. While your DS is 'x86_64', DDSM is considered as 'dockerx64'. Every SPK package has an INFO file, which has a lists for supported architectures and may or may not have a list of excluded architectures.
You could try to download the spk of your choice (Index of /download/Package/spk
), rename the .spk to .zip, use a tool of your choice to edit the INFO file inside the zip and modify the entries for "arch" and "exclude_arch". Then rename the .zip back to .spk and try to install it in DDSM - since the signature for integration checking can not match the modified spk anymore, you need to make sure you can install unsigned packages. You can lookup the architectures here.
Such a modified SPK package may or may not run if dependencies are not baked into DDSM like kernel modules or required tools.
Anyhow: better try and fail, than not trying at all.. best case you succeed, worst case you just lost a couple of minutes of time