How to copy and paste as plain text on iOS?

Solution 1:

At least in iOS 13:

1. Select the text
2. Don't tap "copy" but instead "share..."
3. Tap "copy" from the share sheet

This copies without formatting. Works at least in Safari and Mail and probably many other apps.

Solution 2:

In Mail on iOS 12, I use the "Share > Copy" trick:

1. Paste formatted
2. Select the just pasted text and in the context menu swipe right and tap on "Share..."
3. In the Share sheet, tap on "Copy". This copies as plain text!
4. Tap still selected text to get the context menu again
5. In the context menu tap on "Paste" to replace the selected, formatted text with its plain text representation

Still (too) many hoops to jump through but at least you don't need to switch between apps. The "Share > Copy" trick might not be available in other apps, though.

Solution 3:

I just tested Shift+Option+Command+V and it will paste without formatting on iPadOS 13.4.1