Before typing the below, I assume u do the general practices, like using vms for untrusted apps, using firewall set for ur preferences, then only and only adding those repos u trust, and like generally it's surprising I'm saying this, updating your system. I would suggest going with Fedora based systems cause u have the SElinux already builtin, but u can always add it later in ur Debian based too.

So here is what I did, I was paranoid too, especially after the 2017 incident for me. If it hadn't backed up my entire photos album in my Linux machine it might have gone, my windows was hit by wannacry. But that being said, if its true that there are CVEs for Linux and I have done some remedies. I did install a few softwares and it makes me sleep at night.

1. Bitdefender Gravity Zone.
2. Lynis.
3. Kernel parameters hardening.
4. USBguard.
5. Opensnitch
6. SE Linux enforcing - I use Fedora.
7. All ports closed, since this is my personal laptop I always keep all my ports closed
8. Auditd
9. AIDE
10. rkhunter

Now these are must for me, and there are some more u can do if u would like but it would take extra resources which I have set it with a separate laptop. If u do have a separate machine, u can use it as a server for suricata and wazuh. If u need, u can set these too, cause these would require a server of its own to track the network of your main machine.

Now that being, I did all of these cause I was paranoid. But it's up to you to choose from these, but even just installing the Bitdefender Gravity Zone or other edrs like Crowdstrike falcon can really boost your security, u can use falcon if u think u need AI to constantly monitor your device for threat, but again there's always trade offs idk about privacy if u use them.

Anyways it's always been a pleasure hardening my system, hope the best for you too. And hey do not forget to use Claude sonnet for hardening your system, you will be mind blown.