I suspect October will not be a huge deal. If a nasty exploit does pop-up in the wild I strongly suspect MS will back patch it for the next year probably.
You also split your intended audience and every discussion. It’s one of the big issues with Lemmy and federation right now. People create multiple copies of the same community across different servers.
Out of curiosity, is your phone number real or virtual ( like Google Voice) Many services won’t send to virtual numbers anymore because they’re used for scams so much.
Yeah, VPN at the very least adds another hoop they have to jump through.