There’s a whole anthology book about this written by a bunch of big and small names, the pdf is free https://machineofdeath.net/ebook

Take a look at keeb.io, they have a few full size splits https://keeb.io/products/quefrency-rev-5-pcbs-hotswap-65-65xt-split-staggered-keyboard

The whole premise of the book is returning to earth, but The 100 starts out in the way you’re wanting including multigenerational space stations and resource limitations.

I am using the pi hole for DHCP, maybe you just have to turn off the DHCP server on the att modem.

I know what we’re going to do today!

Are you sure about that? I’m using the official AT&T fiber modem (Nokia white oval) and a pi.hole for DNS. I do remember needing to change a number of settings to get it to work though.