freamon

The API provides it, which means that many of the clients will also have a way of displaying them.

Your instance provides an alternative UI via the ‘Photon’ client at https://p.feddit.org/ - you can use this on desktop to view your profile and select the ‘Upvoted’ view.

The command-line equivalent would be
curl --header 'authorization: Bearer LOGIN_TOKEN' 'https://feddit.org/api/v3/post/list?liked_only=true&page=1&limit=50' | jq .posts[].post.id | xargs -I {} echo "https://feddit.org/post/%7B%7D"
but it’s nowhere near as convenient as getting a client to do it for you.

The other site mentioned - https://lemvotes.org/ - doesn’t use the API and is a bit controversial: it tends to be used to see who else voted for a post, and isn’t guaranteed to be a reliable way to show what posts you personally voted for.