I had been retired for medical reasons & spent some time at bible college taking along an old Compaq Portable (80286 with 5.25" floppy) to take notes on. It was about ~1998 so my heavy box was a little dated, but it worked & I couldn't afford to replace it.
A guy at the college (Whitley) suggested I check out ComputerBank who gave out refurbished laptops with GNU/Linux on them (Debian). I went along and was given a much more modern Dell laptop which used 3.5", had a battery, and most importantly didn't weigh a 'half-ton'.
I'd read about GNU/Linux in trade/tech magazines, but had never used it before, and had little to no interest in it (seeing it as a toy created by hobbists). (I'd worked in IT, but in a closed source shop using old big blue boxes). On using this donated dell though; it sure felt like the unix I'd used years ago at university. I still didn't care for the kernel (Linux), but I loved the GNU (GNU's not Unix), so I only touched GNU/Linux distributions (Debian said GNU/Linux back then).
It wasn't until ~2010 before GNU/Linux became my prime OS; it's been that since; and I stopped using only GNU/Linux distributions. It's the only OS I now use on my own boxes.