I followed the doc to get me started with my librem key. When I reached the section about heads I got stuck, because it reads
Using the Librem Key with Heads
TODO: This section will be incomplete until we finalize the initial Heads UI. In the mean time this blog post describes how the Librem Key integrates with Heads The Librem Key Makes Tamper Detection Easy
I had to search the forum to get the hint that there is documentation for coreboot/heads that contains how to enable heads with the LibremKey.
This should be referenced in the LibremKeys documentation also.