4Day GPP-Hypertrophy: HBBS is Painful - LBBS ok?

Doing 4 DAY GPP Hypertrophy. Day 3 calls for high bar or safety squat bar. I am a wuss when it comes to high bar - smashing of the traps is too painful for me. Gym has no SSB, and there seems to be one pad in the whole gym (and that is often missing). I presume I can just do low bar?

That is fine.

I used to be in the same situation doing LBBS basically throughout my whole training career and then trying and finding out that HBBS are a real PITA. I came back experimenting with them on tempo squats one day because I figured the weights were relatively light and my low back really got fried during LBBS tempo squats. What I then figured out was that I was actually trying to carry the bar too high up the traps. Try experimenting with the empty bar carrying it a bit lower until you find it sitting comfortably. It might take some adjustments to your gripping style as well.