What are the usable hosts on the .128.0/19 network?

This range is incorrect as it implies a different subnet mask or network block calculation.

This range is incorrect; the upper bound .134.254 is not consistent with a /19 network starting at .128.0.

This range includes the network address (.128.0), which is not a usable host, and the upper bound is incorrect for a /19.

A /19 subnet mask (255.255.224.0) means the first two octets and the first three bits of the third octet are network bits. If the network ID begins with 128 in the third octet (e.g., X.Y.128.0), the block size for the third octet is 256 - 224 = 32. This means the network ranges from X.Y.128.0 to X.Y.159.255, making the usable host range X.Y.128.1 through X.Y.159.254.