I think the possibility of an old Mac Mini getting hacked is slim to none, but better to understand the possibility before you start than say "why didn't anyone tell me".
The WPA2 encryption keeps everyone out of your wireless signal, without some sort of encryption your 12 year old neighbor would be using all your wireless bandwidth sharing music on Napster.
But WPA2 encryption does nothing to keep you safe from malicious files or websites. I could send you a friendly email with an EICAR attachment that would freak out your computer and be hard to remove.
https://www.eicar.org/download-anti-malware-testfile/I do a lot of research on a computer and sometimes end up at questionable websites plus my old business email still gets malicious attachments every few days. It's a scary world out there if you know where to look.
Eset Antivirus Log

Malwarebytes Professional Threat Log 09-22-2022
The IP addresses are probably from embedded website ads but I don't want what they are selling

For over a year I have been running Windows 11 on two computers, both are used all day every day and neither has had a lockup or blue screened. Networking has improved too, the 2 computers, Blu-ray player, Pixel 3 phone and Android tablet always connect and stay connected.