EU law doesn't actually require a monopoly for competition rules to apply, it's a "dominant position". Apple certainly meets that definition for smartphone platforms.

https://eur-lex.europa.eu/EN/legal-content/glossary/competit...

Distribution of software on iOS?

Apple and google essentially own 99%+ of the smartphone market, so it's not that different from a monopoly

iPhone apps.

If it helps, think if Windows apps had a 5% Microsoft tax and had to be approved by Apple.

'Monopoly' is the wrong term. It's abuse of market power.