Here you can find the most recent state of Macbook support under linux.
Your model, according to Apple website is MacBookPro16,1 or MacBookPro16,4.
Supossing your model is MacBookPro16,1. On the github site it specifies:
The MacBookPro16,1 currently requires a 5.6-RC kernel and the latest amdgpu drivers.
So I think the issue is that you don't get screen output. Possible solutions involve installing this amdgpu driver manually and updating to a mainline kernel.
Try to boot into any elementary option and press Ctrl+Alt+F1 to open a tty ( console view). Login with your user credentials ( login = your username) and execute
sudo ubuntu-drivers autoinstall. The root password is the same as your password usually.
To install the required kernel, the easiest way is to reboot and do it manually.
Go to the mainline 5.6-RC website and download from the AMD64 version the debs in the 1st, 2nd, 4th,and 6th line (the generic versions basically). Then install all of them with
sudo apt install ./li*.deb. Make sure you open a terminal in the same folder as your files.
For any other issue please refer to the linked github site.