as explained here I showed that the betweeness centrality of a node on the fee graph is proportional to the expected routing fees which again is proportional to the throughput of your node.

So taking your throughput and dividing it by your betweeness centrality score should give you a rough estimate of how much throughput is handled by the network.

That being said. The betweeness centrality is constantly chaning as well as routing fees. Also the entire argument assumes a uniform distribution of sender, receiver pairs (which is highly unlikely) Other than that there are no verifiable sources you can use. You will however find people publishing their logfiles or some statistics. All of that information has to be taken with doubt though

Nodes can choose to publish their throughput, but they can also stay private and go very anonymous by using the tor network for their node, this website aggregate most of the public node data https://1ml.com/statistics as they said:

The statistics are aggregated and calculated from multiple nodes within the Lightning Network. Due to the decentralized nature of the Lightning Network, the numbers observed are approximations and nodes that don't broadcast their state are not included.

If you want to see the live update of one of the public node, just pick one of the most recent updated one: https://1ml.com/node?order=lastupdated