YSK: wefwef is a web app that look very similar to Apollo and works on both android and ios
Why YSK: looks very similar and functions like Apollo, if you're used to Apollo that's a great app for you, even if you do not, it's still one of the best apps for lemmy
You can install the web app here: wefwef.app/settings/install or just use it on your browser here wefwef.app
You just make another account on a preferably smaller instance.
It's a new account though, that means you're not migrating anything.
I expect there will be some tools in the future which allow to migrate/sync your subscriptions between accounts at least but comments and posts will always be tied to the instance your account belongs to, I guess.
I just checked into this, it looks like this is not available on Lemmy as of yet. It's available on Mastodon, and is an important feature, so it will likely be added in the future.
I would suggest creating an account on your new instance for now, considering it's so early on. In the future I expect this to be added.
You cannot currently migrate your account from one instance to another. You can do so with a community, but not with your user account. This is something being talked about for a future version of Lemmy. In the meantime, there are tools and scripts out there that attempt copy data/subscriptions over from one account to another, but they are hit-and-miss