A clean and updated installation of a Linux distribution, on, for example, a laptop that we do not use, leaving the correct port open and closing the unnecessary ones, is the beginning of basic security. After that we can use many tools, including the firewall (I won't name them since each distribution usually uses a different firewall), and we will have our wallet with above-average security. If the user knows Linux, with patience security can become high. I have installed Electrum on Debian for 7 years and I have not had any problems. I won't say anything about Windows or Mac, since I have never liked platforms with proprietary code and I haven't used them for quite some time.