Why not count those? ARM is much more democratized and is huge. With the advent of compiler backend abstractions being used in LLVM and GCC, it's even possible to target unique chips more easily.

Intel is definitely no longer the monopoly player they were after the huge success of ARM in lower power environments.

Intel has never been a monopoly. There have always been dozens of competitors in most of their markets. Even at the height of Wintel, there was AMD and others. Intel didn't win there because it was able to shut out competitors, those competitors copied Intel designed instruction sets and Intel couldn't stop them from doing it. Intel dominated the market because of their better processes.

From an antitrust perspective, a monopoly is simply a firm with significant and durable market power with courts having typically set that to having over 50% marketshare within a certain geographic area.

Intel certainly qualifies.