A bog standard Linux distribution boots under 30 seconds with a good HDD, assuming hardware initializes fast.

SSD generally adds 3x to that speed due to access latency for small files.

I remember pressing power button and leaving my PC alone to get a tea or something when I was booting my Windows installation which I had around for gaming. Same with an SSD. Desktop arrives faster, CPU still choked to launch whatever services are needed, fans are doubling as hair dryers.

Both scenarios were on the same machine, BTW.