I just installed a Curt trailer hitch on my 2020 GLA250. It is to carry my mountain bike on my 1Up bike carrier; I do not plan on towing anything. I read that there have been changes since the instructions and video posted by eTrailer (for a 2017 model). This definitely appears true, comparing them to my 2020 model. For example, for newer models one must cut an inch or more out of the bumper bottom‘s unpainted black plastic trim, but it is not noticeable unless one crawls to look from underneath. Also, 2020 does not require removing exhaust sport tips/squares (i.e. skip this step). So far, I am very happy with the trailer hitch. See below for pics.
My takeaways (as a novice) are to take your time removing all of the plastic pieces required to uninstall the rear facia in order to install the trailer hitch, and then reinstall rear fascia. Also, take a picture of each step on your cell phone (as this can be a lifesaver, even following instructions, and also save you from second-guessing yourself later). Third, use sandwich baggies and stickies to label/group each set of screws and snap pieces that you remove, where they go, etc. Fourth, it took several hours for me to do with my dad. While one could probably do it a lot faster, if one is über meticulous like me, it’s worth it to take one’s time (to not scratch/break, not miss something). Fifth, make your you have all of the tools required, some of which are special (e.g. various torx keys, torx ratchet sockets, crowfoot wrenches, plastic removal tools, and flexible socket extension cables). Lastly, one must watch the video from eTrailer, read instructions, and also watch a Mercedes video on removing the rear area interior lip/base to access two additional bolts (to remove rear fascia).
Viel Glück mit deinem GLA250 Projeckte