Just disable "Secure Boot" and try Trisquel, then see what happens.
I recently tested a Skylake barebone (HP Pro Desk 400 G2). To my surprise, everything works excellently under Trisquel or deblobbed Debian. It is true that Skylake's integrated graphics and audio require non-free firmware. But without these non-free firmware they still work fine (with acceptable graphics performance). The WLAN adapter I installed is an Atheros AR9462 (M.2 form factor) so it works fine, too.
I gave said barebone to my local community. They said that it was possible to neutralize the ME using "me_cleaner", and this means that there is no Boot Guard enforced (The CPU is replaceable). Additionally, starting Skylake, VT-d feature is supported by both CPU and chipset. IOMMU is available even on this lowest-end H110 platform.
