hi,
there are some points you need to consider:
1. s32ds includes supporting for some kinetis chips but it supports KEA only. s32ds doesn't support MK20DX128.
all the supported devices are listed on our website:
S32 Design Studio IDE|NXP
2. do you use NXP demo board? which board do you work with? if TWR-K20D50M, CMSIS-DAP doesn't support it.
3. according to S32DS Fact sheets, it only support J-link and P&E interfaces. there is no official solution for CMSIS-DAP interface.

4. if you work with MK20DX128, I suggest you use KDS.
Kinetis Design Studio Integrated Development Envir|NXP
Hope this helps!
Have a great day,
Jennie Zhang
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