For most flows there are anytime returns, off peak returns (somewhat cheaper but time-band restricted) and maybe even super offpeak return (cheaper yet and even more time restricted). Then there are Advances that are only one way and are [mostly] valid on only one specific train. Those returns mentioned are typically valid any train subject to the time-band restrictions and route - and sometimes train company. Bare in mind off-peak does not have a blanket start / end time across the network. To be certain you need to note the type of ticket, the conditions, etc but yes the concept of an open return certainly still exists, albeit that the railway doesn’t tend to call it that anymore. Beware of some returns sold by Trainline that appear to open returns - some are actually tied to specific trains when you read the detail. Some booking sites also insist you specify out and back train times before giving a price, even though the ticket is actually valid on many trains which can be another point of confusion for those not familiar with how things work these days. Simple eh? No, maybe not. If all this makes you confused or concerns, ticket offices at stations will also invariably sell open returns over the counter.
