@lemmy I have account on mastodon.social (as you can see above). I can read Lemmy and write posts via my Mastodon frontend, but it has very limited functionality (ex. I can’t upvote posts or it is comfortable to read long threads). Is there a way to use Lemmy frontend without creating any Lemmy account with my Mastodon server backend?
simply put: no
most fediverse software has its own API specific to how that application works. in some cases different fediverse software may be sharing a common API, which is typically a result of either a reimplementation (e.g. the Sublinks project is working on a reimplementation of the Lemmy API) or the result of a fork, where the previous API has been inherited and is typically built on top of.
It should also be noted that while Lemmy and Mastodon both use ActivityPub federation for interoperation, they have significantly different internal structures for how data is stored and represented to clients. I don’t know if mastodon supports vote federation with Lemmy at this point, but if it doesn’t do that currently, then using an alternative frontend won’t help you. It would likely be possible to build a Mastodon client that has a better thread view though, but it’d still have to be something built for the Mastodon API specifically.