dictation alternatives?

Due to limitations imposed by Apple, there aren't many dictation alternativves. I suggest that you become comfortable with one or more of the other methods of text entry including:
<ul><li>handwriting input</li>
<li>braille screen input</li>
<li>input using a braille display</li>
<li>input using a Bluetooth keyboard</li>
<li>using another device to write notes which you could either send from there or copy to your iPhone and then send</li></ul>

The onscreen keyboard. The most accurate, and built-in, so no other device is necessary.

There is a free dragon app for the iPHONE; it's more limited than Siri but it might do a better job recognizing your voice and you can copy and paste the results in to another app, like a word processor or mail. When I first got my phone I played text adventures with the onscreen keyboard to build up my typing speed. It was more fun than typing things I had to type. I would also say that I find the dictation very accurate but I've had training on using Dragon for Windows. You might look on Youtube for training on speaking correctly to Dragon. Those same techniques will work with Siri. It takes practice, because you have to speak very clearly but not necessarily slower or louder. Try making it a practice to dictate a note at least twice a day in a quiet environment. I often dictate in the notes app. I have watched Siri accurately take dictation from a colleague with such a thick Indian accent I myself have trouble understanding her!

using the fleksy keyboard. After getting used to it it most of the time I have become a rather quick writer. However I really love the dictation accuracy on my Pixel 2 which runs circles around the dictation feature of iOS!

Since gboard isn't allowed to make use of googles stt feature the best bet is a alternative input method. I'd give Fleksy a try. But maybe something else works better for you.

Hi.
If you're having issues with certain things, like new line, period etc, then I suggest typing them. I've had problems with new line the most. Usually, what I do if I'm dictating something where I have to put that in, or some other troublesome word/punctuation, I just stop dictating, and type it on the keyboard and then resume dictation. I use dictation a whole heck of a lot, and I've learned to know/assumme the things that might make dictation trip up. It may take you a bit longer, but I think you'll get used to it.

Make frequent use of on-screen predictions, they really do learn. I particularly like the speeddots protector with them, as each prediction is marked by a dot, making them easy to locate. Dragon Anywhere is a subscription service, but it is highly accurate. It can be set to beep when the microphone is turned off, and synchronize words with Dragon for desktop, if you use it. Like the other app Debee mentioned, text must be pasted into the target edit box, but increased accuracy and less editing may make the tradeoff worth it. I really need to use it more, but I'm impressed when I do remember to work with it.