The good news is you can really appreciate the reason this car was created. When on a road trip, make sure you put it into HV mode. On the highway in that mode, the engine will run from time to time to keep about a 50% charge on the batteries. You can just buy gas as needed. I had no problem driving over 300 miles that way then just topping off with gas to keep going.
This link not only has the owners manual but other info you'll find helpful.
FAQ | 2018 Clarity Plug-In | Honda Owners
Check back and tell us what kind of mileage you got. You can set the computer to re-set mileage info every time you fill up if you like. There are lots of user settings you can do from the main display. Many of them require the car to be stopped and in park to access them.
Most of my driving now is short trips around town so the car is perfect for me. I rarely buy gas now LOL. Last week I did have a contractor install a Level II charger in my garage. Now the overnight 10 hour charge cycle is about 1.5 hours.
Planning on going on a 1700 mile road trip, can this be done without having to stop to charge battery useing the H.V. mode and when battery gets below the level where the H.V. Charge mode can be used?