I don’t see anything in the pictures which looks like a cultivated plant except an Azalea in no 2. There’s a lot of stuff there, some of which are Burdock, Oxalis, Red Clover, Horseweed, Black Medick, White Campion, Dandelion, Sow Thistle, Plantain and Garlic Mustard. Bottom line it's pretty much entirely weeds.

I’m in your zone and the most kemp’s ground overs I have (weed suppressing and neat edges) are pachysandra and geranium macrorhizum.

I, too, do not see anything that looks like an intentional groundcover.

Most groundcovers don't look sloppy as long as they're weed free. You need to get the weeds completely eradicated before installing anything. And after the install, you'll need to police and since you have had weeds (lots of weed seeds) I'd suggest Preen on a schedule, for at least a couple of years. And then you could probably get by with hand weeding if you like.

Vinca minor might be a possibility.

I have pictures of a shady slope covered in geranium macrorrizum, mentioned by another poster here. https://www.houzz.com/discussions/5931811/another-slope-the-cheap-fast-one#n=7

If this link doesn't have 4 photos you can find the original post titled something like "a cheap fast slope" Yes, you have to weed first and keep at it. Preen, double thickness newspaper, round up are options for weed control. My hillside looked like yours. It's not high design now, but its nearly weed free. Geranium macrorrizum is fine in sun. There are several varieties so it doesn't have to too boring.

I have found that G. macrorrhizum definitely doesn't want full sun, especially hot afternoon sun. But closely related G. 'Karmina' or 'Biokovo' will be very happy in full sun; they're a little smaller but otherwise very similar.

re: geranium macrorizzum. Laceyvail, you are much warmer than zone 6a (MA) I grew up in Baltimore and I know from hot. Honest, my macrorizzum grow in full sun here. I came a website called the "impatient gardener" and its column on g.Macrorizzum. The author is in zone 5 in Wisconsin and she grows it in the sun. I grant you that on a 90 degree day in dry soil they don't look as good as in the shade. But generally I find the big roots do fine. I think it's gift is that it thrives and flowers in the shade.

I used to have a zone next to my name. Some where I lost my zone on Houzz.

Strangely, I find that G macrorrhizum wilts even in my pathetic northerly sun. But it always recovers at night.

floral, do all or just some or one wilt in the sun> May be the g macrorrizum just don't read the same books we do. I say just buy a couple, try them and if they don't work put them in the shade.

G. macrorrhizum definitely doesn't want full sun; hot afternoon sun really is hard on them. For full sun use G. 'Karmina' or 'Biokovo'.

I have both Karmina and Biokovo in half day sun and they do very well in those conditions. Last season I tried moving some of them to my front bed that is full sun all day. I'm questioning whether that was the best decision, because they are looking stressed. Red edges on the leaves, lighter green. They are blooming. They are on a slight slope near the street, so I keep thinking it dries out more there, so I keep watering every time they look dry. That doesn't seem to be making a difference. I think next year will be the test, once they have settled in and had another winter.

another vote for macrorrhizum in full sun (with loam)

in summer we get temperatures from 96 -102 and in a long dry spell they start turing yello but usually bounce back.

G x cantabrigiense Biokovo is even more draught resistant in my beds/ area, but has not as vigorous rhizomes, I would say.

if it is really hot and sunny and the soil on the poor side, Biokovo probably outgrows most plants as it is like a low-calorie marathon-runner

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the weeds on your slopes look like mostly annual and some perennial, but I did not spot couch grass or bind weed.

so just some quick weeding with a hoe should do the trick before planting, and mulching perhaps while the plants establish their root systems

Thank you all so much for your input. You’ve given me a lot to think about. I’ve decided that my first focus needs to be wiping the slate clean. I’m starting by hand weeding/digging

because the bank is close to my neighbors and I want to avoid spraying roundup... and I can use the exercise anyway.

My plan after that is

1) preen

2) Black tarp

3) ... wait.

Anyone have input on if this would be effective/how to ensure the best outcome?

Progress pic of what I’ve managed so far this morning. I tried to dig the trampled burdock you see to the left out; it’s clearly prehistoric because those roots go to China.

The "progress" picture did not come through. Allow it to become full color before submitting it.

FYI, I use a fan tip on my sprayer which gives a knife edge sharp spray line, which is easy to control in tight spaces such as along lot lines.

Some black plastic does not actually cut out all light but dims it way down, allowing some weeds to survive. Make sure that would you use doesn't permit any light to come through it. (Harder to do than one would think. It might require some multiple layers of certain materials.

how about now?

It looks more do-able than the first pictures. Keep in mind it's all going to try to come back. Be ready for the attack.

Cardboard. :-). It will last a whole season.

Update: