Regarding Secure Boot, that’s definitely a problem. However, not all distros support it OOTB. I might have dismissed it earlier because I consider FDE to be more important than Secure Boot. But I’m aware that this is not on technical merits.

I’d consider FDE more important as well (apart from some fringe use cases). But it doesn’t cover all possible attacks, as unlikely as some of them are. However, together they create a solution that is both convenient and sufficiently secure, as long as you can’t just intercept the keys on the hardware.

FDE protects the confidentiality of your data in offline attacks, Secure Boot protects integrity and authenticity of binaries started by UEFI. These complement, they don’t compete.