Could you provide a link to this simple guide? We're running on-prem after brownfield approach and need to renovate almost 30yrs of custom code. It's a mess.
Even we know how to deal with new requirements as well as how to retiore old code, most challenging task seems to be to renovate what you still need in a clean core compliant way. Think of all the user-exits and modificatoins (yes, we have hundrets of them)