My trailer has basic solar panels and LiFePO4 batteries, in addition to 12vdc and 110 ac when hooked up to shore power. I want to use an Uno to control color and brightness with potentiometers on 12v LED strip illuminating steps for a relative that has vision issues. It would only be be used at night, so it the batteries won’t be getting charging voltage and amps. The batteries will probably be supplying 13.7 VDC
Do I need to use a buck converter or ?? to provide 12 volts
The datasheets have the part “Absolute maximum ratings” telling what You really need to know.
A nonsense question. You already have 12 volts. A Uno is a 5v device and it's onboard regulator is pretty crude. This means that, irrespective of the data sheet, it is pretty uncomfortable about shedding 7v from a 12v supply. You would be better off using a decent off-board regulator. You are going to need some other peripherals to handle the LEDs.
I had a similar setup on my RV before I sold it. I used a buck to drop to 7V, then a linear to get to 5V. The LED 12V can be connected directly to your 12VDC battery bank (Yes, the voltage fluctuates depending on where in the charge cycle you are, but I never had an issue. If in doubt, use a 12VDC regulator.
Assuming a UNO you need to be careful of the 5V load on the Arduino. If it is just the Arduino and the LEDs are operated off the 12V that should work just fine. This is what a simple search found for me: The Arduino Uno can accept an input voltage range of 6 to 20 volts, with a recommended range of 7 to 12 volts for optimal performance. That has been valid for my UNOs.
If you want to prevent dimming of the LEDs as the battery discharges I would recommend a SEPIC converter as a Buck will drop out of regulation when the batteries get in the 12V range. This will vary depending on the module. The SEPIC should be good for at least 5V to maybe more then 25V. If you use the SEPIC feel free to power the UNO with that output. Be sure to set the output voltage before connecting your hardware.
Fully charged 4S lifepo4 battery has voltage14.4V. While common 12V LED strip likely tollerate that, the life could be reduced.
You could use simply 5V stepdown converter (for both, LEDs and arduino) and 5V ws2812b addressable LED strip. This way you don't need LED driver and as a bonus you can have some visual effects to give more attention.
Hi, @johngillettek8
Welcome to the forum.
Don't forget a fuse(s) in line with the Lipo supply to protect your project.
Tom.... 
Oh yeah, I plan to have one. I have a bunch already. And I put them where I can reach them.
12 v LEDs now, I think I’m just going to go with 5 v strips. Inject power if it seems to need it. They are to illuminate the tongue, steps and awning supports at night and not for decoration. So I don’t need too much power. That will solve most of the challenges. Eventually add motion sensors to turn them off and on.
I’ve got places that I can use the 12 v strips around the house.
Are they the addressable type or is there a separate wire for each color.