There is an API end point to get upvoted posts. I don't know about third party clients, but you can get it with curl
:
curl -H "Content-Type: application/json" -H 'Authorization: Bearer <Auth token here>' \
-X GET 'https://ukfli.uk/api/v3/post/list?type_=All&sort=New&liked_only=true' | jq
> Look up package
> hasn't been updated in 7 years
> install it and it still works
God, I love emacs