Trying to advise someone on FR about turf or plants is an exercise in futility, as soil, weather, and growing conditions in the USA vary to such a great extent.
One person’s dream plant can often be another person’s weed.
The very best option is to consult nurserymen in YOUR area.
New hybrids come into the market every year.
I have been out of the business since 1980.
I see we agree that vinca minor might be his only answer.
Our vinca is blooming right now in upstate NY. It does very well under extreme cold conditions and is quite prolific.
We own a registered nursery that specializes in native woodland plants, mostly ginseng (panax quinquefolium) and Goldenseal (Hydrastis canadensis). I also do site consultations for landowners that want to grow these plants for profit.
Do you miss the business?