This app was mentioned in 13 comments, with an average of 2.31 upvotes
Consider solving many tactics instead of lessons, I believe this is the best tactics app available, no ads, offline cache, has an engine built in...
Chess Tactics by TIMLEG is the only offline one I really like, after trying ALL of the free tactic trainers on Google Play, testing if they worked offline (if you've experience, you'd know most of the 'good/popular' ones only work online). This is pretty much a hidden gem of an application in terms of offline use. Been using it over a year and a half, and have done ~8,000 puzzles.
I don't own one myself, but I'm inclined to agree with u/pinkp0weranger. I'd imagine it isn't as plug and play as it might seem. I'd just say look up some videos of people setting it up on YouTube before spending any money.
Regarding Lichess, since another comment mentioned it; while it is pretty much one tap/click from the lichess home screen, I could see him getting lost on the app if he struggles with basic internet browsing.
As someone who's been in a similar position to your own (without the chess) I'd highly recommend really showing him how to use whatever tablet/computer you get him (navigating the home screen, returning home, closing/suspending/reopening apps) and make it clear to him that he's not going to break anything. A lot of older folk are too scared to mess around and learn what stuff does. Just, for the love of god, don't put any payment details/private info on it.
Edit: I'd also recommend this puzzle app if he understands the concept of chess puzzles, since there's no menu and a very clean UI. The only thing I could see him get caught up on is the analysis window (to look at the how the puzzle's solution works) after each puzzle.
Another nice idea, if you're thinking of learning, could be for both of you to get a physical set and play against each other by calling out your moves over the phone. I'm sure he'd appreciate the company at the same time.
I dunno, maybe 60 seconds. I spend a lot of time on tactics, it's the only thing I do on public transport, sadly my lichess score does not reflect it - I'm too careless. If you'd like to improve, I would recommend this android app. Just do it all the time and you'll see stuff like this :)
Do you mean this one? You can use the attached computer engine that shows you exactly why the tactic works. You just need to follow various lines to see what the best continuation is. Often it might just be winning a Rook for a Knight or win a pawn.
This one is best on Android:
https://play.google.com/store/apps/details?id=com.timleg.chesstactics
It shows you the opponent reply if you make a wrong move and lets you analyze the puzzles with Stockfish 6.
1) Learn how strong players analyse positions. Here are some examples:
Notice how they select candidate moves and how they analyse lines. Notice how they always take into account the opponent's counterplay.
2) Bring your tactics rating above 1800
Chesstempo.com is very good. On Android, my favorite app is this one.
3) Play a long time control game (>15min) per day and analyse your mistakes first without an engine and then with an engine.
4) Learn how strong players handle opening, positional and endgame play simply by watching them play longer games on YouTube. Do not just watch passively, but actively think about what moves you would make.
This may be a bit counterintuitive: Don't waste your time playing Blitz games. At least initially. The key to getting stronger in Blitz is not to play Blitz.
Aside from the mentioned, Chess Tactic Puzzles is great as well.
There's an app on the play store called "chess tactic puzzles" that's pretty solid
https://play.google.com/store/apps/details?id=com.timleg.chesstactics
Chess Tactic Puzzles on Android
The puzzle is from this Android App:
https://play.google.com/store/apps/details?id=com.timleg.chesstactics&hl=en
If you are on Android, this one has the best interface:
https://play.google.com/store/apps/details?id=com.timleg.chesstactics