Digital processes differ from regular processes in methodology and metadata. Every business domain has own set of fundamental process elements and their relations. In case of regular processes, elements and relations are more (but not entirely) human-centric. In case of digital processes, elements and relations are more (but not entirely) machine-centric. The border between two is very subtle.
There are hundredths of process methodologies developed to date. Many more are developed now, some for digital processes, some regular processes and some pretending being universal for both worlds. There is no ideal methodology for all processes, no matter digital or not. Ideally, own targeted methodology should be developed for each business domain. In practice, narrow methodologies are often misused and generalized improperly outside of their intended domains. This may happen across digital to human ridge or on other, less significant boundaries. In all cases, it is enough to follow proper methodology and guidelines to achieve consistent models and smooth execution. Division for digital and not digital looks not so crucial in this respect.
In practice, it is unlikely that somebody will ever encounter today a process, which is purely not digital. It must be a workplace and a worker entirely isolated from computer, phone or other means of digital communications for prolonged time. Therefore most of processes in modern world are digitalized to more or less extent even in poorest and less developed countries.