If you are looking for structured chess courses similar to the style of Praful Zaveri (who focuses on fundamentals and logic), here are free and legal resources:
The "Chess Course by Praful Zaveri PDF Free Download" is a valuable resource for chess players of all levels. While it may lack interactive features and updates, the course provides comprehensive coverage of chess concepts, clear explanations, and numerous examples and illustrations. If you're looking for a free, comprehensive chess instructional material, this course is definitely worth considering. chess course by praful zaveri pdf free download
If you can’t buy Zaveri’s book, follow this free curriculum inspired by his method: If you are looking for structured chess courses