I don't get the reasoning behind this. At least in Linux I can easily see what's going on inside of my system and its networking. You shouldn't have to worry about doing banking on it??
I have a i7 2012 mini as well and it's currently running Linux very well I must say. A lot lighter on the system compared to any modern version of macOS, no waiting around for most software to load. I imagine OP's MP wouldn't be slow either.
Linux is a mess of hundreds of millions lines of code submitted by tens of thousands of coders, many of them anonymous. Nobody sufficiently qualified really checks most of that code for vulnerabilities or especially deliberate inserted malicious code. Linus himself has a rather dismissive attitude towards security.
Here’s what Graphene OS developer has to say about Linux security (read more towards the middle of page)
https://www.reddit.com/r/GrapheneOS/comments/bddq5u
If I was in charge of a government espionage agency, I’d plant a group of highly qualified hackers behind an .edu address at some well regarded college, have them submit high quality code to the Linux foundation or various other open source components like drivers for a few years until they develop a good trust based relationship with maintainers, then inject a carefully hidden malicious code. And if I can think of this - definitely the right people in the US, Russia, China or North Korea aren’t any dumber than me. Surely this could happen on Windows and MacOS too, but the free-for-all nature of Linux code contribution makes this a whole lot easier. As the fairly recent UMN scandal very nicely illustrated, the entire ecosystem largely runs on trust. And the spy agencies have been caught abusing this.
Bvp47 of yore said to have used BPF to conceal comms in network traffic
www.theregister.com
Now, you may say “well spy agencies aren’t after my data, I’m not a big enough target for them”. But North Korea, Russia, Iran and other sanctioned regimes are employing large groups of hackers to steal money anywhere they can - including private accounts - because these funds can’t be traced back to them and thus make it easier to subvert the sanctions.
Once, FASTCash ran only on Unix. Then came Windows. Now it can target Linux, too.
arstechnica.com
And of course it’s not only the spies, it’s could also be criminals or even some malicious person with patience and good enough coding skills. Linux makes it much easier to inject your own code than either Windows or Mac.