macOS as many times more secure than the Linux desktop. The only reason Linux is not a malwarefest is because the market share is so small that it is not that interesting.
[1] https://0pointer.net/blog/brave-new-trusted-boot-world.html
If any government has backdoors in macOS outside open source software in macOS, it is probably very limited (the US government if any, but Apple seems to resist most attempts at weakening security).
[1] https://arstechnica.com/information-technology/2010/12/fbi-a...
That’s much harder with open source software, not due to technical reasons, but because there is a good chance that eventually it will be discovered by some developer or security researcher. That will cause distrust of the government, and people going to defensive mode, making it much harder for governments to routinely hack into devices.
So, for example, the discovery of the flaw in the Debian random number generator had a huge impact. People who design security systems really pay attention to PRNGs nowadays (to the point that it seems weak PRNGs are no longer a significant concern in the mainstream desktop operating systems, though the issue obviously remains in IoT, virtual machines, HSMs etc).
Hiding the code for malware is common sense. That’s also why governments severely punish leaks these days.
But when thinking about state actors they almost have unlimited money/resources thus even if adding a backdoor is a bit harder on open source having unlimited money/resources makes it irrelevant.
Where “unlimited” = to the size of the open source organisation that maintains a bit of software.
It's easy to detect backdoors in closed source applications.
People should definitely be using open source for as much as possible, because I want to live in a world that makes it as easy as possible for beginners to understand how their underlying software systems are working. The whole "backdoor" FUD just seems lazy though.
No reason to make your life harder unless you’re doing it for your own enjoyment.