What package manager do you use for your Linux machine?

Apt also.

I don't know if it's a 'Which came first, the chicken or the egg?' situation but I have concentrated over the years with Debian and Ubuntu based distros. They use 'apt'. So do I use 'apt' because I prefer Debian and Ubuntu, or do I use Debian or Ubuntu based distros because I prefer 'apt'?

It's probably a bit of both. I started to use 'apt' because I used Debian and Ubuntu, and now I prefer to use Mint Mate, and have done for around 12 years, because it has 'apt' as its main package manager.

I use apt, and one for every bloody language I code in (except C)