Alby and ZBD support this already. There is also a meta tag for HTML: https://github.com/BitcoinAndLightningLayerSpecs/rfc/issues/1
Both could be crawled and indexed.
It's probably way simpler than you might think.
@dergigi @adam @dave with a little bit of redirect magic (one line in nginx) you can also use a nicer domain: https://github.com/btcpayserver/btcpayserver-doc/blob/master/docs/FAQ/LightningNetwork.md#how-to-redirect-a-lightning-address
Bitcoin Maston Instance