I currently have a Let's Encrypt SSL certificate in place on my site, and everything is working correctly. However, I am now wanting to install a dedicated GoDaddy certificate instead.
My server setup is Apache on Ubuntu. Is it possible to install the new certificate and keep the Let's Encrypt one registered as a fallback, or do I need to entirely revoke the Let's Encrypt certificate first?
Yes, you can even keep both simultaneously. Apache will send whichever it likes more. (depending on the negotiated parameters of the tls session, and if the certificates are actually different)