Hello,
you are correct that SDK is available in Linux version of S32DS, but it has never been tested in Linux operating system and it does not completely work correct in Linux operating system. This is applicable for all versions of S32 Design Studio.
I have no idea, why is SDK available, when it is not tested and it is not compatible with Linux.
About your question I.e. may I install SDK updates targeted for v2.0 onto 2018.R1? Or just stick to v2.0.
No, this is not possible even in Windows versions. Every update is determined for some version and also, it is not possible to install older version of SDK into newest version of S32DS, because of some dependencies and Processor Expert tool. (This is applicable for Windows and Linux version too).
Regards,
Martin