I think this is not really the place for full ethernet introductions.
For the PC (Linux) side, I would go for the socket interface, and UDP.
Do a search, there are plenty of basic-level tutorials and explanations available.
I suggest to not skip this reading.
And there are plenty of ethernet examples for Linux, for your receiver application.
Cube and the H7 are not my thing, though.
But once you have a general understanding, check for limitations of the lwip ("lightweight") stack on the STM32 side.
