I've had my Liberte since January. I changed the gearing to a 54 tooth chainring with narrow/wide teeth, the derailleur to an old Ultegra 9 speed I had in my spares, Ultegra 12-27 9 speed cassette, KMC 9 speed chain and Altus 9 speed trigger shifter. The narrow/wide chainring eliminated the need for the plastic chain guide and guard - I've had no problem with the chain jumping the chainring. Going to a larger chainring doesn't let you use the smaller chainring cover anyway. Shifting has been smooth and I like the range of gearing I have - I ride mostly in my middle cassette cog (17 teeth, I think). I have experienced some creaking in the stem as well, but it's not too bad.
I bought the chainring on AliExpress - delivery took about 3 weeks to the US. This is the description (I can't post a link yet): VXM Road Bicycle Narrow Wide Chainring 130BCD 54T 7075 Aluminum Alloy Ultralight Chainwheel. Current price is about $17.
The stock chain should work with up to a 54t chainring.
Hope this helps.