I read somewhere that this happens primarily in a browser address bar, because they've tuned the keyboard in that context to strongly prefer dots over spaces. I'm not sure if that's true but I have also found that it happens to me the most when doing multi-word Google searches from the address bar, and not anywhere else.

Also, I used a couple alternative keyboards a few years back, but I have found that some point some iOS update within the last few years made the stock keyboard the best for me. When I type on the gBoard on my wife's phone it might as well be dvorak, everything comes out gibberish.