Native Plant Gardening

You're generally not going to find many native plants in big box stores (or often you'll find non-native varieties of native plants); online shopping is really your best bet for seeds, and local garden shops (vs national chains) for starts.

For your region, Prunella vulgaris aka selfheal, is a good option for scatter-and-forget. The plants are a little shorter, so they will grow in mowed grass lawns like clover does, although if they're not mowed they'll get to about a foot tall (this means they may struggle to survive if planted among tall grasses/shrubs). Each plant produces many seeds each summer, so the seeds are small and plentiful. The purple flowers are small but pretty splashes of color. In my region (PNW) they are evergreen. On the taller side, Chamerion angustifolium aka fireweed, is another easy-grower. It grows 4-6 feet tall and produces stalks of lovely pink flowers that bees absolutely adore, and fun wispy seeds in the autumn. The plants die back entirely every autumn and resprout in the spring, propogated by both root and wind-blown seed. They make lovely clumps that are good along fences or a sunny corner of the yard, and can grow in more crowded meadow-like conditions. My final recommendation for a seed-scattering choice is lupine; there are many lupine varieties so make sure you get the right one for your area. It looks like Lupinus perennis aka sundial lupine is native to most of PA and is a smaller, more manageable variety (some lupine varieties can get to be 6+ feet tall and just as wide!). Bees also love lupine flowers, and lupine are less wild-looking than selfheal or fireweed, in case you have neighbors who care about that kind of thing (lupine are popular garden flowers). My final recommendation is Asclepias syriaca, aka common milkweed. This is a critical plant for monarch butterflies (it's the only plant the caterpillars can eat), but it has questionable benefit for other insects so don't plant it in isolation. It also is toxic, so keep it away from where children or pets play. The plants die back in autumn and resprout in the spring. All the above recommended plants produce many seeds every year (and many are perennial or will resprout from established roots) so once they've gotten established you should be good to go. I know you said you want to be hands-off, however giving them a little help during their first year will greatly increase success rates; this means clearing away competing vegetation and watering during dry spells (as well as being strategic where you scatter seeds, rather than blindly yeeting them wherever).

In doing this research I stumbled across https://www.keystonewildflowers.com/, which is based in SE PA; I'm sure they have additional recommendations for you!

Generally for toss-the-seeds species I recommend spreading the seeds in the autumn (you can try a few handfuls once a month from August to October) to best simulate what happens in nature. You can also try again in early spring (March and April). Some plants (e.g. milkweed) require a cold cycle before the seeds will sprout, while for others it doesn't seem to make a difference. Where you sprinkle the seeds makes a big difference; most flowering plants like sunlight, and too much competition from tall grasses/shrubs/trees will prevent growth.