Some thoughts from the perspective of bee life cycles and flower relationships. I’m in central Europe, but I imagine most of these points also hold true for the northeastern US.
Except for social species like Bombus and some of the halictids, most wild bees are proterandrous, meaning that the males (like the Andrena in your photo) appear a week or two before the females. What this means is that for these really early bees, nectar is probably more important than pollen – sustenance for a hungry newly emerged or overwintered bee rather than provisions for offspring.
Bees that collect pollen only from a small range of plants are not bound to the hosts plants for nectar in the same way.
One of the bee specialists here writes that Galanthus is not a particularly good source of nectar; this fits with my own observations, which is that the bees here don’t seem particularly interested in snowdrops even when these are much more plentiful than other options. Scilla and Muscari, by contrast, are very well received – I would be more concerned about removing these than Galanthus. Eranthis is happily visited but around here it seems to be just about over most years when the solitary bees are starting to emerge, so it is only useful for a fairly short period.
I’m not very familiar with what native species might be good candidates in Pennsylvania. Using phenology annotations on iNat is likely to only provide a very incomplete picture because so many observations are not annotated. You might try looking at observations of bees in March/early April and seeing what they are visiting, though this may give you a lot of non-natives.
Salix is fairly important here as a nectar and pollen source for many of the spring bee species. Some other plant families that include relevant early-blooming species are:
Allium, Asparagaceae
Berberis
Asteraceae
Brassicaceae (preferably large-flowered species)
Lamiaceae
Rosaceae
Boraginaceae
Campanulaceae
Caprifoliaceae (Lonicera, Symphoricarpos)
Cornus
Ericaceae
Fabaceae
Veronica
Primula
Ranunculaceae
Viola
I’ve been pondering similar questions about what I can put on my balcony this early in the year. We had several really warm days last weekend and as a result the bees have started emerging, but there isn’t a lot that is blooming yet. While native plants would obviously be preferable to introduced ones, I think there are some arguments for flexibility, particularly when climate change and weird weather may be upsetting previous phenology patterns (with the potential that bees and flowers might not be completely in sync).
Many of the bees that I’m seeing are also urban bees – meaning that they are those that have adapted to the conditions of cities, which in many cases may offer more plentiful flowers (parks and cemeteries and even garden centers) than they would otherwise normally find this time of year.
I planted both round leaf and sharp lobed.