Hafele is what most pros use. LED tape. With driver.

Here are a couple of useful videos. The second will help you choose a diffuser, the type of which is important to avoid LED hotspots or stars reflected in the kitchen countertop. Remember also that you will have to select a color temperature for your LEDs. (I like 3500K for a kitchen.) I recommend a driver (aka transformer) that's compatible with a wall dimmer e.g., Lutron LED+.

https://www.superbrightleds.com/ is a good source of all things LED (tape, channels, diffusers, drivers, etc.).

• LED Strips, what's the difference? WS2811, WS2812B, 2812Eco, WS2813, WS2815, SK6812, SK9822
• I bought every LED Diffuser channel on Amazon to find the best one. Mission Accomplished. (Just ignore the dancing girls at the beginning.)

“none have been bright enough.”

Make sure you are installing them in the correct location. UCLs should NOT be installed toward the back, but they often are. When UCLs are installed at the back of the upper cabinets, they are lighting mostly the backsplash. UCLs shoukd be installed toward the front of the upper cabinets so that they shed light onto the center of the counter beneath them.

Have you been checked for cataracts? Most LED tape lighting is super bright.

DeWayne, thank you for the recommendation!

wdccruise, I appreciate the videos and the link to superbrightleds, I'm going to look through it!

MMiller, thanks for the tip- we did in fact install lighting near the front of each cabinet.

Monique- you made me laugh! No issues with vision, and all family members agreed it wasn't bright enough. We've seen professionally installed under-cabinet lighting and it's been significantly brighter.