Using the AWSCore::GameLiftServer plugin requires you to install the OpenSSL libraries in your AWS Linux Instance.
install.sh Example
sudo yum -y install openssl11-libs.x86_64
sudo chmod u+x ./GameLift_Server/Binaries/Linux/GameLift_ServerServer
Uploading GameLiftServer
The most important part here is that you use the AMAZON_LINUX_2 type and not the default Amazon Linux Instance.
copy install.sh d:\_compile\AWS\LinuxServer\
aws gamelift upload-build --name GameLiftServerTest --build-version 1.0.0 --build-root D:\_compile\AWS\LinuxServer --operating-system AMAZON_LINUX_2 --region eu-west-2