Or, you could continue your brave forward-looking journey and try one of the Fediverse Solutions for Insta (namely Pixelfed) and leave Marks torture cellar behind.
Problem there is that you need to move many people at the same time to work (extremely hard) so your friend would be there while in Lemmy you dont need friends just content
Unless, of course, Meta is lying. Threads will be federated and Instagram will likely follow, meaning any instance dumb enough to not defederate them will be able to interact and follow users without an Instagram account.
You can't delete a thread account that is created without also deleting Instagram account. Someone reported seeing that they were following people that didn't have threads accounts yet so Meta might be creating shadow accounts for Instagram accounts that haven't taken the plunge yet.