What's the solution to malware and virus?

There are anti-malware packages for Linux. I generally haven't felt the need to use one on a desktop. You're the biggest security risk to your PC; don't go to shady websites, don't download anything suspicious, etc. Your email provider will run a virus scan on email attachments for you (if they don't, get a new email provider).

On basically all Linux systems, software is installed from central repositories, basically the app store model. Packages are cryptologically signed to verify their source, it's a lot safer than the Windows model of "just download and run a .exe from the vendor's website."

The old argument of "no one runs Linux so no one writes Linux viruses" doesn't completely hold up to scrutiny, but on the other hand a lot of attacks that would be meaningful to desktop users are indeed written with Windows in mind; malware you'd run on Linux tends to target server applications that you probably won't run.

All the options and sub-options for installing and managing things feels so daunting!

This will become less of a problem with time as you become accustomed to the Linux ecosystem and discover the native ways to do things. On a system like Linux Mint, there's a thing called the Software Manager which provides an App Store like interface for finding software from both the standard repository and from Flatpak/Flathub. You may find that there are options from both, what I tend to do is just try them both and keep the one that is more functional for me. Give it a try in a virtual machine or from a liveUSB to see what I mean.

Microsoft does things like have Windows fuck up the bootloader on purpose so they scare you into not trying to take ownership of the computer you bought so they can keep abusing you. If you're too scared to break your main computer that you rely on, maybe go to Goodwill or eBay and pick up a cheap old used computer to experiment with. Grab an old laptop or something. I learned a lot about Linux using Raspberry Pis, which I didn't rely on for anything so it might have been inconvenient if I broke anything but not mission critical, I could just re-flash the OS and be on my way, though these days it's probably easier to just pick up an old used machine and maybe stick a cheap SSD in it. That freedom of "this isn't a precious machine to me, if I kill the OS I can just reinstall it" makes you more willing to try learning things.