There are many websites (such as chess.com and 365chess.com) which allow even a free account holder to practise a certain number of chess puzzles on a daily basis. However, I feel that most puzzles are about tactics instead of strategy, such as winning a piece, forcing checkmate, etc. Am wondering if there are (preferably free) online resources that allows one to daily train strategy (such as how to improve your position in a silent game, or create a weakness for your opponent) which does not necessarily resulting in immediate winning of material or checkmating. Any recommendation will be greatly appreciated.
It is relatively easy for these websites to generate many thousands of tactical exercises: they run an engine over a corpus of games (for example, games played on the site itself) to look for blunders, and then turn the punishment of the blunder into a tactics puzzle (usually after additional filtering for example to choose only positions where there is only one move that is clearly best). They don't even need to worry about grading the puzzles for difficulty, because they determine that empirically after the fact, based on the ratings of the users who are able to solve the puzzle or not. The leave it to users to flag dubious machine-selected exercises for review.
The same is not true for strategy puzzles, since strategy is not so clearcut that you could let an engine search for strategically interesting positions. Therefore, strategy puzzles need to be laboriously created by experts. I know chess.com does have a "lessons" section, but you need to be a paid subscriber if you want unlimited access. Many of the lessons are about strategy, for example Roots of Positional Understanding by IM Jeremy Silman has 300 hundred brief "challenges" which you could use as daily puzzles for a while.