Airtight isn't really the best way to describe it. Rather it's controlled air exchange, this way instead of 1000 tiny leaks all over you have a central controlled means to exchange air.
Passive home typically have ERVs or HRVs (Energy/Heat Recovery Ventilators) to achieve this, they can control the heat/humidity in the air.
Came here to say exactly this. I've setup family members with Samsung "Commercial Displays" for their TVs and haven't been disappointed. The display is high quality since it's built for a more demanding purpose, but it also means none of the consumer friendly optimizations exist for easy color balance. Essentially this means you've got to bring your own device and do some configuring, but since we're on selfhosting that's something you were probably going to do anyway.
An additional note - the models I got also still had RS-232 ports for direct control and some newer ones included control commands over ethernet (even when powered off), making it even more fun for smart home shenanigans.
Most passive houses I've seen have windows that open, but they are typically double/triple glazed (depending on climate) and are casement style instead of the more typical (and inefficient) double hung. They also typically feature a ventilation system to manage air movement precisely to prevent the issues you're concerned about.