https://minesweeper.online/

I play there regularly. Requires connection to internet (compared to http://minesweeperonline.com) and the board generation is server-side. Although there are hints available (they cost a currency), they take a few seconds to calculate, they are percentage based, and you cannot play while that takes place, so simply sending a link to the game may be enough if there's no way hints could have been used (by looking at how fast the player plays). If there were any pauses in someone's play, they would have to submit a live video of solving the board.