Exactly. Open source means by design there are more people able to look at the code and therefore more emphasis for those interested in the code to want to make sure it works securely. You can be exploitative and try to keep your hack secret but there’s also a chance that someone else will see the same thing you saw and then patch the code with a PR. Granted it depends on how much the original developer cares about the code to begin with to then accept or write in a patch/fix for the vulnerability that someone else brings up but the example software you listed are larger projects where lots of people have a vested interest in it working securely. For smaller projects or very niche software that have less eyes and interest, open source might not be the most secure.

On the closed source side, the people who are interested in looking for hacks are the ones who are much more motivated to actually exploit vulnerabilities for personal gain. The white hat hackers on the other hand for closed source software are fewer because not having the code available openly means they have to have more motivation (ie the company offering bounties/incentives because they care about security) to actually try to work out how the closed source software works.

BIOS /UEFI malware exist too. Your suggested best practices should also factor this in. Basically if you’re being targeted there’s nothing you can do but by being aware of these risks you have a better chance to keep yourself safe.

As a living thinking being it’s your own responsibility to think about what’s important to you and what you want from life. Being in your circumstance is outside your control. You could have been born into a kind/cruel family or a fortune/unfortunate one and have an easy/comfortable life but I see it all as luck. If you were born in a different body with certain brain chemistry you’ll think about life in a more carefree or dutiful way. Imagine that for any person you can possibly conceive and potentially any creature or even bacteria that don’t or can’t think in such a considered way.

With all that in mind you’re probably pretty lucky in the circumstances you’re born in and you have been raised to be empathetic or you were naturally inclined to be but if that’s how you are you can choose to continue those values that try to help others to live in a positive way while you still can. Maybe there’s a reward or not. For the conceivable time you’re able to be empathetic and cognizant of your place and privilege maybe you’ll find happiness in knowing helping others can bring comfort and joy to others and in turn yourself. There’s no knowing what is after but choosing to spread decency and altruism within your means can give you comfort that when the time comes (however soon or sudden) you can end knowing you were gifted and gifted a blessing to the other lives you contacted who may also continue in your footsteps.