How many devices can join a video FaceTime call (if they are laptops or android devices)?

Thank you for the reply TuanAnhTruong. We'll be happy to clarify further. We will be pulling information from the following article, along with the Group FaceTime article linked above:

Use FaceTime with your iPhone, iPad, or iPod touch

You can connect up to 32 total devices in a Group FaceTime call. This includes sending a FaceTime link to non-Apple devices. You will need to make sure you initiate the Group FaceTime call from and with a device that fits the system requirements listed above first. Then, you can send invitation links as needed to your additional participants.

Start a Group FaceTime call from the FaceTime app

1. Go to Settings > FaceTime, and make sure that FaceTime is on.
2. Open FaceTime and tap  New FaceTime.
3. Enter the contacts you want to call.
4. Tap the Audio button  or  FaceTime.

You can add up to 32 people to a Group FaceTime call.

Then:

Create a link to a FaceTime call

1. Open the FaceTime app and tap Create Link.
2. Tap Add Name, type a name for the meeting, then tap OK. This lets others know which call they're joining.
3. Select the person you want to send the link to, or send the link from Messages, Mail, or any other supported apps in the Share menu.

You can invite anyone to join a FaceTime call, even people who don't have an Apple device. They can join you in one-on-one and Group FaceTime calls from their browser. You can't create a FaceTime link with Windows or a non-Apple device, but you can join a FaceTime call if someone shares a link with you.

Have a good day.

Hello TuanAnhTruong,

Welcome to Apple Support Communities. We'd be happy to answer your question about Group FaceTime calls. You can add up to 32 people, but that is only available within the FaceTime app or the Messages app. This is available for non-iOS users.

Read more about Group FaceTime here: Use Group FaceTime on your iPhone, iPad, and iPod touch

"To use Group FaceTime video calls, you need iOS 12.1.4 or later, or iPadOS. on one of these devices: iPhone 6s or later, iPad Pro or later, iPad Air 2 or later, iPad mini 4 or later, iPad (5th generation) or later, or iPod touch (7th generation). Earlier models of iPhone, iPad, and iPod touch that support iOS 12.1.4 can join Group FaceTime calls as audio participants."

Have a good day!