A paper from 2020 co-authored by Christian Decker shared that 10% nodes hold 80% liquidity:

LN: A second path towards centralization of the bitcoin economy - https://arxiv.org/pdf/2002.02819.pdf

Liquidity in 2024: https://mempool.space/lightning/nodes/rankings/liquidity

Maybe someone could write another paper with present stats including use of custodial wallets