Several alternative app stores for iPhones and iPads are already in the works as Apple prepares to open up its iOS ecosystem to third-party software providers under new rules enforced by EU authorities. Software company MacPaw is among the first to announce plans for a rival app store, called Setapp Mobile, and Apple users in the EU interested in the new app store can sign up on a waitlist for the beta version, MacPaw says. So far the company has not said when exactly the store will go live or what it will look like. MacPaw already offers a software subscription called Setapp with a number of …