Been working on this on and off. video poker trainer for 9/6 jacks or better, free, no signup needed to play, no ads, no real money. Just wanted something I could practice on without any other garbage on the site.
After every hand it tells you whether you held the right cards. If you didn't, it shows you the optimal hold and roughly what the mistake cost you in coins per coin bet. tracks your accuracy across the usual strategy buckets like high pair, four-to-flush, three-to-royal, etc., so you can see where you keep leaking. There's also a drill mode where you can pick a bucket you struggle with and just hammer hands matching it until it sticks.
If anyone finds a hand where the recommended optimal play is wrong, let me know. That's a bug and i'll fix it. bonus poker, deuces, and ddb are on the list but i wanted to get 9/6 jacks rock-solid first.
https://www.jacks-or-better.com/
(Should) work well on phone and desktop