Engaging with the DR specialists in your organisation is a good starting point. A DR assessment should be done to see which DR category SAS Viya 4 on Azure falls in to based on your organisation's DR rules. The more business-critical SAS is, the higher the DR standard and category should be chosen. Once that is agreed you can work towards meeting that standard using resources like the link @JuanS_OCS has provided.
Unfortunately there is no OOTB solution from SAS for DR so a DIY approach is necessary. We are in a similar position to you at the moment but with on-prem SAS 9.4. It is a lot more work than you might expect!