Labeling something does not make it a 'social construct'.
We label rocks based on how and when they were formed. This does not mean it has any sociology behind it.
But I do respect your opinion and if you do think so, you are well within your rights to do it.
Sex is not a social construct. Gender is.
It's true - we are learning more about sex every year and understanding it's not completely binary. But your sex is assigned at conception.
That's one of the reasons doctor's don't ask about your gender, but your sex - because treating could be different. And, as an example, IHE (medical standard) recognizes about 7 sexes.
Gender, on the other hand, defines social norms we expect from certain sex. How gender is perceived changes from culture to culture and from one period of history to another - sex doesn't.
That being said, I do believe that gender roles should be a thing of the past. You do you, whatever you're comfortable with.
None of this account for differences in purchasing power and phone price.
If you have an $150 Android device, I would of course expect you to spend way less on software than somebody with a $1500 iPhone.
I'm not saying 'develop for Android only' but if your business relies on one ecosystem only, you're at a higher risk and you're leaving money on the table.
Well, they have limited themselves to single point of failure.
That's like selling only blue shoelaces and then crying faul when your only supplier stops making blue color.
If your livelihood depends on one account only, you are in great risk anyhow.
That sounds like anecdotal evidence. Android is more popular in more than half of the world and a lot of apps are successful and generate income on both platforms.
What do you mean 'Croatia is not even a directly neighboring country anymore'?
Last I checked, Croatia and Hungary still share almost 350 km of border.
Pirate Party in Slovenia did not qualify for elections. They needed the support of 1.000 constituents, but when the officials did the count they only had 970 signatures.
What I'm saying is - your mileage my vary.
In all seriousness, I think I've seen 'Mx' used in this context.
Usually though, you'd go with a generic greeting such as 'Dear Sir or Madam' or 'To whom it may concern'.