FWIW, the research on braintraining apps is not encouraging. There's no indication of any harm from them, but also extremely limited support in the data for anything approaching transfer and generalization of any supposed gains to anything outside of the game. E.g., the original developers of CogMed found that they could improve number span with the tool (which trained users on number span), but that's all it did. It didn't even consistently improve similar tasks, like letter span. In the decade or so since, the data have not really improved, although there are more studies. When you read through the documentation provided by the publisher (owned by Pearson, btw), you'll note that, after lots of optimistic small studies are cited, many of the sections close, almost as an afterthought, with "there is one large study that did not find a significant effect," or similar. Their own research summary document even admits that some of the apparent benefits only accrue to students who do not have working memory deficits! I.e., it's only helpful if you don't need it.
This isn't to say that these types of tools might not be helpful to specific people, of course. But it's anecdotal at best, and might have some placebo-type effects that aren't really related to the actual intervention content. (Since double-blind wasn't typically part of the study design.) And I'm not knocking the placebo effect; its benefits can be useful and real.
So you can try it if it fits into your family situation. It's unlikely to hurt, and there's always the chance that it will help in some way, but I wouldn't lean too heavily on it. I would prefer to see interventions for executive functions that are embedded in the actual school-related tasks that require executive functions, so you don't have to wonder about transfer of skills.
For example, HOPS is a nice practical program, usually managed by a teacher, but also something you could try from the home direction.
https://www.amazon.com/Improving-Childrens-Homework-Organization-Planning/dp/0932955509/Take a look at the work of Sarah Ward:
https://www.efpractice.com/about-5-1Or Peg Dawson:
https://www.smartbutscatteredkids.com/Oh, and if you want to hire someone to do EF coaching, places like Beyond Book Smart have locations staffed by reputable professionals. They do a lot of work with 2e students:
https://www.beyondbooksmart.com/
