Hey, I am glad you are interested in making games more accessible too! I was able to implement some accessibility features. This is what I did:
1. using the "read aloud" option on text elements that was suggested by fedca earlier (this only works with a screen reader though, if you want to read the text to everyone, I suggest speech synthesis)
2. making sure the font had a good readability, size and contrast with the background
3. making the font scalable
4. adding easy language texts (were provided by the contractor) as an alternative to the more complex texts
5. not having excessive effects and animations that could disturb players
6. providing a portrait mode (the screenreader useage gets messed up when you rotate the phone in landscape mode)
7. this was the biggest surprise: using the html buttons
Html buttons are already quite accessible, e.g. they are "seen" and read aloud by the screen reader, without any extra checkbox like for text elements - they will be read aloud at any time though, they can't be "hidden" like when you place an element outside the viewport. I'd need to check the project again to see how I solved this.
Html buttons also can be accessed by using the tab key on the keyboard helping ppl who don't have a mouse. Screenreader useres also use the tab key to navigate. Note: your elements should be in an order that makes sense to tab through. I had some struggles with that, but again, I'd have to check the project to see how I solved this. I think the solution was to make a layout plan BEFORE I put the elements in and then creating the elements in the order they are supposed to be accessed (e.g. buttons and texts in the upper left corner first, buttons and texts in the lower right corner last).
What I could not provide: a scrollbar that is accessible with the keyboard and with the voice control. I used the ProUI plugin which is easy to use, but unfortunately not good for accessibility out of the box. In the next project I want to experiment with the iframe instead of a text element to see if that could work - it already comes with its own scrollbar. I also could not add alt text to the images, I would have had to come up with a custom solution. Since the images of the project were not super important to the useage, just eye candy, we did not provide alt texts.
I hope this helps, let me know when you have any questions and good luck!