Looks like for iOS this is still in beta, so you will need to install "testflight" from the appstore (allows to install beta apps) and then go to https://testflight.apple.com/join/xQfmkJhc on your iphone/ipads browser and accept the invite link. Then you can install mlem, start it and log in (dont forget to type in the address of your instance at the top)
Trying memmy now for the first time, ty for the heads up. I like some of the design better than Mlem, but there are def quirks that need to be worked out on both. Nice to see this much interest in developing for Lemmy!
If you are on this post : click on the name of the community at the top (above the post title). Then the community opens and you can click "subscribe". In some communities you need to be approved, then you see "pending".
Highlighting text is a pain. I've realized you can't tap or swipe the cursor to select more. You can only swipe over text and hope you got it all. This is still an alpha build in active development though.
If you joined lemmy.ml it was probably because of the instance being slow. You can always create an account on a less popular instance to avoid that issue. I don't think it's Jerboa specific.