The app that synchronizes multiple lemmy accounts so you can migrate and keep backup accounts across instances, it’s opensource and free, currently working in android and windows.
It’s in homologation now and anyone can test, any feedbacks are welcome as always.
If you find any bugs please report
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Same thing happened to me, it seemed like it didn’t do it when I had just two accounts, but it did do it when I had 3.
Not sure if it has anything to do with certain communities not being federated to the other instances