+1 LibreOffice Base It was my first entry to GNU/Linux, LibreOffice and Databases.
As a lawyer I managed all my clients and cases with it. It was a rather pleasant experience. It was easy and I am mexican and english is my second language.
I learned a lot with The Frugal Computer Guy. He teaches LibreOffice (all of it) and some other nice thins of software libre. Like GNU/Linux, Stellarium, Thunderbird, etc
He has a Youtube channel and a website. I link the Base tutorial and the website:
https://www.youtube.com/playlist?list=PLy7Kah3WzqrEerJ0VPNWVaR4CYHMr4wmV https://www.thefrugalcomputerguy.com/index.php
