OGO automatically provides a Let's Encrypt SSL certificate and manages its renewal.
You can also upload your own certificate. This way you will be able to activate the certificate you want.
NB: OGO selects the most strict TLS advanced configuration (Version, Cyphers,...) supporting all the top browsers that generates 99,9% of the Internet Web Traffic.
For 2023, the lowest spec browsers are Win 7/IE 11 and Safari 8.
Solution 1: CSR & certificate upload
You can generate a CSR via "Create a new CSR" and have it signed by your certification authority. Then upload the supplied certificate.
Solution 2: Upload a .p12/.pfx file
You can upload a p12 or pfx file via "Import a certificate".