@sixsous here is the official list https://joinmastodon.org/apps personally I use Tusky. I've also tried Twidere, which lets you have twitter accounts and mastodon in the same app if thats something you're interested in.

On iOS i think ppl have had success with Amaroq.

when you're logging into the app if it asks you for "instance" or "server" you just need to put okapi.website