Many keyboards, on iOS and Android, have a one-handed mode that shifts the keyboard toward the right or left edge of the screen, so you can reach all the keys with a single thumb. On iOS, you'll usually find this option by holding the globe icon and enabling one-handed mode. On Android, it can vary from keyboard to keyboard. Google's Gboard, for example, lets you switch to one-handed mode by holding down the comma key. It won't make typing on a phone enjoyable or anything, but it'll at least save you from making so many typos.