Are you noticing that a specific chat is missing from your Beeper's WhatsApp Space, but is visible on your WhatsApp native app Inbox? TL;DR: That chat is probably a WhatsApp Community chat.
Why don't I see a WhatsApp chat in Beeper's WhatsApp Space?
The question is simple: it must be a WhatsApp Community chat.
According to WhatsApp, Communities allow users to organize and bring related groups together under one umbrella. If this is the case, you should see this chat on the Beeper's Sidebar (no matter the Beeper client).
If it's not the case, please, let us know on your Beeper Help chat, along with comparison screenshots between Beeper and the native app.