No personal experience with this, but I agree that True Leaf Market is actually a name that comes up a lot!
Based on the reviews I've seen and heard, they're generally a reliable choice, particularly for popular, fast-growing varieties.
I think many people report high germination rates for their pea and sunflower seeds.
The hit-or-miss feedback you're seeing is common for certain varieties, especially the more delicate or slow-growing microgreens like basil, which can be a bit trickier to get going no matter the seed source.
I heard True Leaf Market often posts germination rates and specific growing instructions on their product pages, so try checking that as a good reference before you buy!