you can setup your own instance and block federation with instances that way. then use a tool like this to auto-subscribe to all the top communities. https://github.com/Fmstrat/lcs.
I’ve just done that myself for different reasons but this is a discovered side effect.
I found the ansible instructions from that same guide pretty easy if you wanna give those a try. feel free to DM me if you get stuck. Here’s an install support chat too: https://app.element.io/#/room/#lemmy-support-new-instance:discuss.online