There is absolutely no indication or error output anywhere to indicate why this button is greyed out.
I have started the installation using the bin installer: atlassian-confluence-6.12.2-x64.bin
According to your docs, this installer also installs the required JRE (but I have also tried to install Oracle JRE java version "1.8.0_191" with same results)
Operating system is headless Ubuntu server 18.10
I have installed MySQL Ver 14.14 Distrib 5.7.24, and configured it as per https://confluence.atlassian.com/doc/database-setup-for-mysql-128747.html
One Issue here which may be the source of greyed out "Next":
Your manual says to execute this command in mysql:
GRANT ALL PRIVILEGES ON <database-name>.* TO '<confluenceuser>'@'localhost' IDENTIFIED BY '<password>';
....but nowhere did your installer gave me the password it created for the confluence user it created. So how must I know what it is?, and if I change it, how will Confluence know what it is?
Anyways, I have also installed this JDBC driver "mysql-connector-java-5.1.47-bin.jar" by copying it to "/opt/atlassian/confluence/WEB-INF/lib/" and making it executable: (NOTE that I had to create the directories /WEB-INF/lib/ as they did not exist)
sudo chown confluence:confluence mysql-connector-java-5.1.47-bin.jar
sudo chmod 755 mysql-connector-java-5.1.47-bin.jar
I have also tried making confluence a sudo user:
sudo usermod -a -G sudo confluence
I did restart the confluence server after putting the driver file there.
It is also VERY unclear from this web page:
https://confluence.atlassian.com/doc/configuring-a-datasource-connection-937166084.html
if the steps on this web page is ONLY for a JNDI connection or if the steps for Tomcat etc should also be done for a JDBC connection.
So how do I get passed this issue?
How do I get what is bugging Confluence to keep that "Next" butt grey?