There are a few offshore options that do. IC Markets SC accounts can trade a limited number of assets sort of 24/6.5 as they have some weekend downtime for a short while. But you can take advantage of their raw spreads. Another genuine 24/7 one is CedarFX that seem to have a growing rep. Seen some bits on them in other forums and seem ok. As with choosing any broker though DYOR and test them out on demo or use a small capital to start with.
There are a few brokers that have Crypto trading 24/7 .
EagleFX CedarFX Exness Hugosway Kotx and LonghornFX.
I personally use EagleFX for margin trading BTC LTC and on occasion Doge .
As previous poster has stated use a demo account with each and as Crypto can be quite volatile small lots small risk until you find your feet trading it