We mostly use Debian GNU/Linux (best choice) and few more (Ubuntu family)
Focus on Security and Stability for Linux, macOS, Windows, Android, iOS, Web
Hardware/Software choices based on you own needs (Business and Private)
After the first two years as freelance, in 1995 came the opportunity to be IT Department Leader in an important Profit company related to frozen food. Hardware used: server, clients and automated machines for food transport, weight and packaging. Software used: Windows (mostly CSB-System) and Unix (VAX) based.
Finally, after many years with Macintosh and Windows, started the first professional experience with Linux in a big Nonprofit Organization: Legambiente. Proud of that work in the biggest Envirenmental Nonprofit Association. I set up 5 physical servers and many clients (in mixed network for local and remote working) and many many thin clients with Linux. A nice and important work for the head quarters in Lombardia and Milano. I also set up the huge Linux Web and Mail Server legambiente.org
Start SGDM with the official IT VAT Number. More enhanced freelancing services for IT related projects: System Administrations for Linux, Macintosh and Windows; Clients/Servers; Firewalls; Developments; Communications and CopyWriting; Seminars; Graphics; WebSites; SEO (Search Engine Optimizations). All of that for Profit and Nonprofit.
Expansion in highly customized services more and more Open Source for Profit and Nonprofit. Mostly related to security, stability and productivity.