Is there such a problem as b-Matching with different b values?
I'm not sure if it's a standard problem, but it seems this problem is described in Solving the Many to Many assignment problem by improving the Kuhn–Munkres algorithm with backtracking.
(the other closest things I found are https://en.wikipedia.org/wiki/Generalized_assignment_problem and https://link.springer.com/content/pdf/10.1007/BF02190106.pdf, but they are talking about one-to-many assignments).
Anyway, you can solve it using maximum flow. For $b=1$ (usual matching) you can check these slides, namely this picture:

I.e. we create auxiliary vertices $s$ and $t$, create edges $(s, u)$ for all $u$ in the left part and $(v, t)$ for all $v$ in the right part. All edges have capacity one. By solving maximum flow on this graph, you'll find maximum matching (Note: you have to find an integral solution, i.e. where flow through each edge is either 1 or 0, but standard maximum flow algorithms will do that).
For $b&gt;1$ the graph is the same. The difference is that all edges $(s,u)$ have capacity $b_L$ and $(v,t)$ have capacity $b_R$.
If your edges have weights, then you can negate edge weights and solve min-cost max-flow on this graph.