I am a professional electrical engineer and amateur musician.
I first started to see the cracks in equal temperament when tuning a guitar to pure fourths and a third. At the time, I didn't know the source of the error in the pitch of the high E, or that it was called the Syntonic comma. I thought maybe the intonation was off on my guitar.
I first learned in earnest about tuning theory as a university student. The pianos in the rehearsal rooms at my university were badly out of tune. I got tuning tools and learned how to tune by ear. (I also learned a bit about "well" temperaments.)
I'm mostly interested in just intonations, but not exclusively.
Here is a Well temperament I devised and the spreadsheet used to calculate it.
! Cosine C Well.scl ! Kloba's Cosine Well C 12 ! 94.65884 196.61384 298.56884 393.22768 500.52384 593.22768 698.56884 796.61384 894.65884 1000.00000 1092.70384 2/1