I am in the same situation
My Software Engineer son introduced this to me (he beats the snot out of me!):
lichess • Online Chess
FREE, Open Source, & Ad-free!
Spartan interface - just what is needed without gimmicks or googahs. Focuses on the play, not the display.
Appropriate for all skill & experience levels.
iOS 10 compatible. Apple App Rating: 4.4/5
Play offline against a very good AI, or Across-the-Board (in-person opponent)
Online play & tournaments, with Leader Boards.
Move annotations & game summary, with server computer analysis.
Daily practice puzzles (I fail all except the easy level puzzles, but getting better)
Skill rating tracking.
Variant games.
Source code available (for hardcore nerds like my son).