Maybe something like this foil-backed gypsum board, https://www.goldbondbuilding.com/products/drywall-panels/foi...

RF/sound blocking drywall for SCIFs costs a small fortune, https://www.quietrock.com/products/quietrock-530rf

EMF shielding case study, https://www.zokazola.com/emf_reduction.html

You can get a lot of sound proofing by double layering drywall with an air gap in-between in exchange for some floor space.

My apartment ceiling has a ~60cm air gap with air conditioner ducting and stuff inside, not sure how responsible it is but I hear basically nothing from above me. Same for the side walls although I believe those are just super dense fire proof walls.

I suggest the opposite - it will enable many exciting smart home possibilities which in some could seriously reduce HVAC energy needs beyond what’s possible today.

You could leave the internal walls RF transparent. Which allows you to do whatever you want without your neighbors wifi scanning you.

Building energy efficient homes also does that. No need to over complicate the situation.

Lot easier to deploy WiFi in existing homes than build new one. It’s about easy impact on the world.