I believe Wogomite mentioned this awhile ago but I wanted to open up a new topic about it. Heroic Battle is an app that is free and can be downloaded on computer and phone (I have it on both) and the phone/PC experiences are pretty much exactly the same. It has both singleplayer and multiplayer game options and even claims to be able to be able to service multiplayer without a connection to wifi, although I've never tried this. I've also clicked on the multiplayer but never gotten a match after searching for quite some time.
As for the singleplayer (which is all I use the app for) Heroic Battle is in partnership with Probe and that is their singleplayer computer. For any of you who don't about Probe, Probe is a very solid singleplayer bot, far, far better than the computer here. Probe has three difficulty settings in Heroic Battle: sergeant (1 sec move), Major (3 sec move), and General (5+ sec move). I downloaded Heroic Battle over a year ago actually but never thought about it until I saw Wogomite mention it in another thread. I played probe once on all three settings and won all three games. I would say that the "sergeant" mode is about 300-350 ELO, as it doesn't understand the two square rule very well and may allow you to capture say a colonel or major with your gen when Probe's marshal is revealed.
For example, in this: https://imgur.com/a/Qb42DH7 situation, once probe's marshal is discovered and you approach with your gen on Probe's known maj, col, etc. It won't make an effort to move the scout out of the way even if it allows the colonel to retreat all the way back to the marshal. Similarly, it may also not run away with its gen until it's too late once you've captured Probe's spy and corner Probe's gen with your marshal.
As for Major, it's not bad but not great either. I'd say 375 or 400 tops. Still makes some of the same mistakes but seems to use the 2-squares better.
And for General, I was quite impressed with this game mode. Randomly from behind the lake during the midgame I walked into his setup with my unknown col and he hit it with his unknown general even though he also could have attacked it with a capt or major near the general. On General mode, Probe has decent intuition regarding your pieces but still doesn't have quite 100% grasp of the two-square. I'd say that it may be fairly easy to snag say a capt with your col in the mid or endgame as a result of the two-square rule. I'd put probe's "General" feature at around 425-450 but no more than 500 ELO- sometimes it depends per game.
There's also a leaderboard with top 1,000 players' rating playing the computer. Acheivements, win streak, and number of wins account into your leaderboard ranking.
I'd recommend everyone give Heroic Battle with Probe a try and see how you like it. Keep in mind that Probe says that it was "improved" when it was implemented into Heroic Battle and is better than when it was a standalone app, so I'd also like to see what ELO rating you think probe is at for all three features. Good luck!