If you are on Android, use or Shelter apps. These create a "Work Profile" on your phone. You can install Facebook inside the work profile, which is isolated from your main profile. You can log into a temp account here without the main app knowing.
Do you really need to create an account? Sometimes, you can bypass the need for a temp account entirely. create a temporary facebook account hot
A real person doesn't sign up and immediately join "Buy and Sell Crypto" groups. A temporary account acts like a tourist. A real account acts like a lazy resident. If you are on Android, use or Shelter apps