What would be a good suppressor for a G17L is no different than what would be a good suppressor for a G17 and you you would get a lot better response in another forum.
I can tell you that perhaps surprisingly, a pistol with a tilting barrel recoil operating system (almost all of them) and a long barrell will function better/more reliably than a short barrelled one becuase the distance or angle the barrell has move vertically to unlock is less and the leverage effect of the weight of the suppressor will be less.
I'm not subscribing to this thread and I encourage you to ask the same question in a different section.
Less expensive and 6db louder dry but almost as good as evo when wet = www.gem-tech.com Trinity 9 $630 with liner inertial coupler (this is needed for the glock to cycle the slide, and is pre-built into the evo).
I want the evo9 but may have to settle for a trinity.