JAC I can help with this, yes. A good selection of those steps can be ignored, but as you are self-hosted on a VPS, there are a number of steps that need to be taken to get this to work. It may also be the case that we need to swap out Apache for NGINX in terms of the web server back-end, but we should only do this if it's necessary.
We will need an exported copy of the cert you are using - the full chain. This needs to be uploaded to the website in a path where Flarum can see it.