"As currently proposed, Secure Boot impedes free software adoption. It is already bad enough that nearly all computers sold come with Microsoft Windows pre-installed. In order to convince users to try free software, we must convince them to remove the operating system that came on their computers (or to divide their hard drives and make room for a new system, perceptually risking their data in the process).

With Secure Boot, new free software users must take an additional step to install free software operating systems. Because these operating systems do not have keys stored in every computer's firmware by default like Microsoft does, users will have to disable Secure Boot before booting the new system's installer. Proprietary software companies may present this requirement under the guise of "disable security on your computer," which will mislead new users into thinking free software is insecure."

https://www.fsf.org/campaigns/secure-boot-vs-restricted-boot...