Desktop linux isn’t the same as Android, which is why I said the “Android security model”. Android is a mobile operating system and must protect against the fact that it will be in unknown environments all the time. It must protect against physical attacks, software attacks, and partially sandbox apps. Root breaks app sandboxing and allows for modifying system files and reading internal app storage. The system image is immutable and modifications/settings are made on top.
Linux desktop isn’t more secure out of the box. The general user account shouldnt be a sudoer. Immutable OSes are more secure and help pervent rootkits and other attacks. PCs are most often stationary and stored in a private location. Laptops are weak against attacks because you can boot to a different OS from usb without passworded BIOS. Desktop OSes are the geared for the same kinds of protections.
There is good reason why Android is far more secure than Linux mobile.