What's the alternative closest to the completeness of Instander at the moment? I have been using the last version of Instander still supporting v7a which is v16.0 for many years now and as it seems there is a chance it will finally stop working soon.
FediLab is an explicitly general Fediverse app, though it's not designed for lemmy. There's also plenty of native cross-fedi support, as all activities are translated into ActivityPub events.
Frankly I'd recommend a separate app for Lemmy-likes and Mastodon-likes. The difference between following communities and following accounts seems to result in a lot of jank, if crammed into one app.