You talked about the block size debate but seems to have missed that since segwit the space available for transaction is up to a theoretical limit of 4mb, (closer to 2mb)

There has barely been a need for developing and stress testing the lightning network since in the last 4 years the network fees have been around 1sat/bytes (5-10 cents per transaction).

Here's another trustless scaling solution, different but somewhat similar to lighting.
https://bitcoinmagazine.com/culture/building-on-taproot-payment-pools-could-be-bitcoins-next-layer-two-protocol