Honestly the puzzles on chess.com are better than lichess. The lichess ones just seem to have limited scope, I'm not sure why.
That said the interface is good and if you're finding them too easy then your puzzle rating should be rising to the point where it's offering you puzzles you'll find more challenging.
I'm at 2100 puzzle and they seem to sort of level off.
Over the years I've been bitten for weeks at a time by a bug that fetches a batch of puzzles at a time on mobile, and then loops through those 50 puzzles repeatedly instead of fetching more.
Even when not bugged, this behavior of 'fetch N puzzles at once' heavily encourages rating ping pong, you get a batch of easy puzzles, get them all right so your rating jumps more than it should, then a batch of hard puzzles and get crushed. I found I only ever progressed on lichess after grinding meaningful improvement slowly on chess.com, then coming back to lichess to 'catch up my rating'.
I also quite like Chess.com's Puzzle Rush.
Mostly it was not helping to improve at my level at all, they were sort of pointless exercises in my level. What helped were chess king exercises apps where you solve simple situations that are not even puzzles.
But they are common in game and made you start noticing opportunities and own mistakes in game. E.g. at super beginner level, you improve a lot.