The Apple brand has an alternative, but for most people the alternative is "Google" (for phones) or "Microsoft" (for 'proper computing'). I think I've got a Blackberry around somewhere, but the OS is so old it doesn't work with current-spec HTTPS. I've got some Pi's with Linux (and even RISC OS) on them, but I'm also a software developer, alternative OSes aren't what normal people want to spend their free time learning how to use just to get by in society.
If you want to work with others in an office environment, you're using either Microsoft Office or Google Docs for your spreadsheets, word processing, and presentations, because even the really good document compatibility of Open Office isn't quite good enough.
If you want to communicate with others at all, there is at least still email and webpages — those have not yet been totally subsumed by Gmail, Facebook Messenger, WhatsApp, DMing on X, etc. — but even then, not being available on major platforms is considered weird and eccentric and many potential contacts will drop you for that.
(Anecdote about how little effort normal people are willing to put into tech: When I first moved to Germany, I tried to set up a local SIM card. You need to register your identity when setting up the card around here. There is (or was) an app/website for that. On my first attempt, the website customer support people thought that I couldn't use a Mac to talk to them even though I was at that moment using a Mac to talk to them and they knew it. Also they thought that their SIM cards only worked with Android.)
