Restricted Boot (so-called 'SecureBoot') does not improve security. It is nothing but trouble. It's meant to trouble non-Windows users. In dual-boot setups, SecureBoot is a recipe for disaster because Microsoft keeps erasing or tampering with the boot sector, to paraphrase an associate
The real solution is, disable "secure boot" or "SecureBoot" while it's still possible. [...] Just like submarine patents, a lot of this problem was "hibernating" for a while