On an iPhone or iPad, how can I prevent the numbers & symbols keyboard layout from switching back to the letters layout when I press the spacebar?

I would like to be able use spaces in numbers and formulas, but the keyboard layout always switches back from numbers & symbols layout to the alphabet layout whenever the spacebar is used. Is there a way to prevent the spacebar from always returning the layout to letters?

As a very brief example, attempting to enter “1 + 2” would cause two automatic switches back to the alphabet keyboard, while typing “1+2” all mashed together wouldn’t.

I’m using iOS 16+, English (US) QUERTY keyboard, iPhone & iPad. (I thought there was a setting but I can’t find it now… it could have been many versions of iOS ago.)