I am not satisfied with Linux's security and have been researching alternative open source OS for privacy and security
So far only thing that's ready to use is GrapheneOS (Based on Android) but that's not available on desktop (Though when Android release Desktop mode it may become viable)
Qubes OS is wrapper around underlying operating systems, so it doesn’t really fix for example Linux’s security holes it just kinda sandbox/virtualize them
OpenBSD is more secure than Linux on a base level but lack mitigations and patches that are added to linux overtime and it's security practices while good for it's time is outdated now
RedoxOS (Written in Rust) got some nice ideas but sticks to same outdated practices and doesn't break the wheel too much, and security doesn't seems to be main focus of OS
Haiku and Serenity are outright worse than Linux, especially Haiku as it's single user only
Serenity adopted Pledge and Unveil from OpenBSD but otherwise lacks basic security features
All new security paradigms seems to be happening in microkernels and these are the ones that caught my eyes
None of these are ready to be used as daily driver OS but in future (hopefully) it may change
Genode seems to be far ahead of game than everything else
Atmosphere And Mesosphere Open Source Re-implementation of Nintendo Switch's Horizon OS, I didn't expected this to be security-oriented but seems like Nintendo has done a very solid job
There are of course different attributes of an OS design that affect different aspects of security depending on your threat model.
Are your application programmers malicious, or is all application code trusted? Are your users malicious or are they trusted? Do you need to guarantee physical security of the device? Is the device manufacturer malicious? etc.
Different threat models will result in designs that optimize for different types of security. Console OSes for example will tend to be designed around copy-protection of the software, assuming the user is malicious.
Secure from malicious app programmers (Unlike what other people think open source doesn't equate safe, even reputable essential ones can be malicious like recent xz one)
Secure from remote attacks and botnets (Only reason this haven't been a larger problem is because linux desktop users are too few to worth targeting, though that may change with rise of steam deck)
Physical integrity guarantee and protection against manufacturer while nice are very hard to get in current climate
proper sandboxing and permissions, auditable code and small attack surface as opposed to spaghetti code glued together that's impossible to audit, regardless of threat model those things are needed, even linux is moving in that direction (Though very slowly and very half baked like with flatpaks)