The channel liner is one of the dumbest and most obsolete parts on a Glock. I'm sure there will be some others who will disagree, but I'd ask them to consider the fact the liner is completely absent on the older Gen 1 guns, and noone ever had an issue. The 42/43 and 43X/48 also do not have a channel liner, and noone is having issues with those. Rarely do you have to even fool with them unless you are refinishing the slide or assembling it for the first time.
But you still have to use it if your Glock had one to start with or the gun likely will not work, which the 23 does. It's there to provide self lubrication for the striker assembly. Without it on a slide that requires it, the striker will not line up correctly with the breechface, resulting in possible damage to the striker.
IMO, I'd recommend a steel liner. Super easy to install and remove by hand and without damaging it, a little bit of friction with a dry bore mop and it comes right out, and can shrug off the high heat of curing if you ever have your slide refinished, whereas a plastic one can warp and you have to destroy it to remove it. Also works wonders for the trigger.