i use the chessable site and train 1001 chess exercises for beginners and tuning your chess antennae
for me, an online tactics book is more practical than a print version (though print versions are still really good)
the structure and selection of tactics is really helpful vs the random nature of the tactics trainer
nevertheless, the puzzles section on chess.com allows you to practice specific themes and problems you have missed- it is still a good feature
but i found a good tactics book that really hammered the fundamental themes and progressively involved multiple themes helped set the foundation
I have an iPhone and a Mac.