I opened a support ticket and this was the reply:
Hello,
Thank you for your interest in the Nik Collection 2018 by DxO.
We are aware of the font issue on 4K monitors, this was an issue that arose with the previous version of the Nik Collection. Our developers are aware that this is an important fix for our customers, and are working on the compatibility with 4K monitors. We do not know when this will be completed, but please know that this is an issue we are aware of.
Regards,
Florian - DxO Customer Support