Here I think you're wrong, if nothing changed in the last weeks then we have the following popular exchanges accepting LN:

- Bitfinex (see here
- OkEx
- Bitnovo (leading Spanish exchange)
- FixedFloat - Changelly-like exchange
- HodlHodl - P2P
- Paxful - P2P

OkEx and Paxful have added it in the last months, while Bitfinex accepts it since 2019 or 2020. There are a lot of other smaller exchanges and services, see this list (in Spanish) and this website. Kraken seems to be in process of adopting it, although I'm not up to date about the current progress.