I've got your docker to work with OpenID against Azure AD, works very nice!
But it was something odd I had to do for get it to work, not sure if I did it wrong or not?
For it to work I needed to enable both OPT_MYSQL and OPT_OPENID, but it still presented the ordinary user/password login.
The solution was rename "guacamole\extensions\guacamole-auth-openid-1.1.0.jar" to "guacamole\extensions\a-guacamole-auth-openid-1.1.0.jar" so it got loaded before "guacamole-auth-jdbc-mysql-1.1.0.jar". Maybe it's a better way to do that?
Thanks for your work!