Linux kernel is clearer on your question
https://docs.kernel.org/admin-guide/hw-vuln/processor_mmio_stale_data.html
First. Nitrokey doesn’t make CPUs nor chipsets. It is important to know what it is. For x230/t430/w530/t530/we are talking about ivy bridge.
And those are not vulnerable. When looking at Intel, they provide information for non EOL products nor microcode updates for them, which is confusing but doesn’t help understanding the issue.
I would invite you to reply and quote parts on referred article to clarify pieces needing more information.