Rivnuts from Homestead, PA on 4/20/2024 8:38:55 PM:
The following campgrounds have hot showers:
Gap Trail Campground - West Newton, PA
Uniontown KOA - Connellsville, PA
Outflow Campground - Confluence, PA
Ohiopyle State Park - Ohiopyle, PA
Maple Festival Campground - Meyersdale, PA
Frostburg Trail Inn - Frostburg, MD
Cumberland YMCA - Cumberland, MD
C&O Bicycle - Hancock, MD
Brunswick Family Campground - Brunswick, MD
These are all pay-to-stay outdoor camping facilities. I'm unaware of any free campgrounds with hot showers. The campgrounds themselves and other amenities vary from site to site.
Other forum contributors may know of others in case I missed them.