Columbine. Wild columbine emerges early in the growing season and forms intricate red blossoms that resemble hanging Chinese lanterns. This is a good choice for planting by maples. The survival rate is lower when planted directly under a mature maple’s canopy, though it grows well in the dry soil at the edge of a tree. It is common to see the first group of pollinators going nuts for columbine flowers!
Solomon’s seal. Solomon’s seal adds both height and drama to the shade garden, growing in a tall arching manner with bell-like flowers that form under the stem. Because the roots are rhizomes, they can compete in the same soil as fibrous tree roots. This grows well planted at the edge of a maple’s canopy. Planting directly under the canopy yields mixed results. Variegated-leaf (non-native plants) are also widely available for an added bi-color interest.
Ferns of many varieties grow well under a maple. It is important to note that despite the wide variety, ferns are descendants of the tropics, a hot and wet environment. When planted in a dry environment they tend to grow smaller and spread slower, so it is ideal to plant most ferns in a moist and warm location for optimal performance. Ferns such as sword fern can survive in the dense shade of a maple.

Do not add soil to cover the exposed roots as this will damage your tree.

Gardening within the root zone of a large tree is always a challenge, especially one like the Liquidambar (sweet gum), or maple with an extensive network of surface and feeder roots. The roots outcompete smaller plants for any available soil moisture and nutrients and the tree when in leaf will often shield rainwater away from reaching the underplantings. Never raise the soil level under a tree or shrub, especially a well-established tree. As for planting underneath a Sweetgum or maple. try native sedges and native plants that like partial shade.

https://extension.oregonstate.edu/catalog/pub/ec-1521-practical-lawn-care-western-oregon