I thought downloading and redistributing tiktok videos was against TikToks TOS?

Which you only agreed to if you have an account (and even then they realistically can only ban your account). If you rehost publically you might get issues with copyright laws though.

Understandable, trying to move friends and family between platforms is an herculean effort.

For everyone else interested in XMPP, you might want to check out:

• Snikket as a Server (intended to run on a cheap VPS): https://snikket.org/service/quickstart/
• Conversations.im as a Client: https://conversations.im/
• ejabberd/prosody if you want to setup your own from scratch
• this compliance scanner which checks for (probably) the most common extensions for a chat server: https://compliance.conversations.im/

No better alternatives around though if you want to own your data, have proper multi-client support, and at least the option to federate.

What about XMPP? What can Matrix do, that XMPP cant?

Besides that point: why tf do they even crawl lemmy. They could just as well create a “read only” instance with an account that subscribes to all communities … and the other instances would send their data. Oh, right, AI has to be as unethical as possible for most companies for some reason.