This is standard behavior for most browsers when they encounter a self-signed certificate.
Can you get a real certificate? Have you looked at https://letsencrypt.org? Their certs are free, they are easy to install and renew with certbot and they work fine with Alfresco (and all your other web sites).
Problem is that you cannot use Let's Encrypt for an internal site not reachable by the name from the internet (the host name looks to be internal). If you are running on a domain with an Active Directory, it should also be fairly straight forward to issue a certificate from your AD certificate authority for your internal system, and since all your clients in an AD domain should trust the AD CA, it would be considered secure.