If you want an adventure bike that is E20 compliant, you will need to either purchase a new bike or search the pre-owned market for a lightly used model manufactured within the last 1 or 2 years.
If you are looking for a new bike, we would recommend paying the high initial purchase price of the twin-cylinder Honda NX500. It is a rather sorted machine in almost every regard and will feel like a nice step up from your single-cylinder KTM. And since you're familiar with the trouble-free Honda big bike ownership experience, the NX500 makes for a logical step up.
If you decide to go for something a little less pricey, then bikes like the latest KTM 390 Adventure models and the Royal Enfield Himalayan 450 are also options worth looking at.
You also have the option of waiting for the new BMW F 450 GS, although its pricing will be similar to the Honda bike rather than the single-cylinder models mentioned above.
A test ride of everything you shortlist should help you make a decision.
