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)