Yeah you can do LN without segwit . It ' s less efficient , and there are some features you won ' t be able to do . With segwit , you can have a 3 rd party watch your channel for you in case your counterparty tries to broadcast an old , fraudulent transaction . The 3 rd party can automatically grab your money back for you . And the watcher doesn ' t even know about your transactions or your balances while watching . That whole feature is pretty much gone without segwit . You ' d have to tell the watcher everything about your channel , and the only thing they ' d be able to do is email you to let you know if fraud occurred . The other main disadvantage to segwitless LN is that channels would have a preset duration . That ' s a pretty big downside . If segwit doesn ' t activate after a long time , we could reprogram some of the current code to work without segwit . I think everyone ' s hoping we don ' t have to as that ' d be a bit disappointing , but doable . As I meme ' d at scaling HK , there are levels of LN we are prepared to accept