You might like Redstone Games' free crossword app. Lots of constructors from all over the world who make the effort to appeal to a global audience. You'll probably recognize some of the constructors' names from the NYT. https://redstonegames.mobi/. Source: 12 months ago

You might also try Redstone Games' crossword app. Lots of famous crossword constructors, lots of puzzles of all types and levels, and it's all free. Link: https://redstonegames.mobi/. Source: over 1 year ago

For free crossword puzzles from established constructors, try Redstone Games' crossword app. You'll find thousands of puzzles, all levels of difficulties, from big names in the crossworld. No subscription needed. https://redstonegames.mobi/. Source: over 1 year ago

My recommendation is Redstone Games' Crosswords Free app for the wide variety of puzzles. Levels of difficulty range from Easy to Hard, and some 5x5 puzzle packs are rated Very Easy, suitable for children and beginners. The constructors make an effort to avoid America-centric abbreviations and clues. All of the constructors are big names in crosswords, so the puzzles are all high quality. Source: almost 3 years ago

I haven't shared a new crossword here in a bit, because I've been happily seeing my puzzles published in the excellent Redstone crossword app, but here's a recent one that makes me smile. Source: about 3 years ago

Https://listudy.org/en does it with spaced repetition. You could import your own study or use a premade one off lichess. Source: 7 months ago

You can browse the various e4 repertoires here https://listudy.org/en. If you're a beginner, you can learn the repertoire by Gotham Chess. Source: about 1 year ago

I have enjoyed using LiStudy https://listudy.org/en. Source: over 1 year ago

An idea: on https://listudy.org/en play "Blind Tactics" - slowly work your way up to higher plies number. (personally, I prefer even number of plies for whatever reason). Source: over 1 year ago

As one can solve puzzles, one may also enjoy exploring opening moves (in short playing a sort of memory game via openings, with the bonus of understanding why a specific opening is played and which structures it brings). Chessable (there is a specific free course that fits well) or https://listudy.org/en or https://www.chessfactor.com/ are great for it. Source: over 2 years ago