You can get a no-load flasher module to replace the regular one, or install load resistors. Google or look on Amazon.com for LED load resistors. Or what I do is use regular bulbs in the front and LED in back. The advantage of LED bulbs is instant-on for your brake lights giving you more safety, there really isn't any advantage for using in any other position on the truck. If you use a paperclip to plug and unplug into the flasher module socket and with a helper notice it works OK, then that would determine the flasher module is not suitable. Wear leather gloves when handling the paper clip in case it gets hot.
Here is a no-load flasher module, but note that I did not try it with all LED lights, I just suspect it will work. It's returnable if it doesn't work out.
https://www.amazon.com/Keep-Clean-10...dp/B00H8KDON0/