Yes amFilm Ultra Glass is glass. Near identical to Whitestone in quality but much better in performance, at less than half the price. mines over 90% accurate....Amazon reviews are great.
https://www.amazon.com/dp/B084VSDG58/ref=cm_sw_r_other_apa_i_rVQCEbKZDPX2T
Look at the Ultra model as that link above is for the regular S20
Best Install vid https://youtu.be/EcSht_KwJJY
Been using since my S10 (after Whitestone did not perform well) and has saved my phones 2wice.
Hey! I don't know if you still wanted this info but I ended up getting the Otterbox Commuter anyway and bought a $40 screen protector off of amazon because this one seemed the least sketchiest. I just finished applying it and it fits well with the case and everything! Also works with the fingerprint scanner :)
Took me sometime to find the right one. This is pretty good. I had my wife install it for me lol.