This is something I'm encountering as an issue while migrating an old WordPress site that used a subdomain for all images. I think my only option currently is to move all images to some sub-directory of the main domain and then run a search and replace in the database.

This would be useful for many non-magento sites as well.

At the moment, support for additional vhost for the sub-domains or pointing to separate webroots is not available.

However a solution for your scenario would be to add 'Additonal domains' through Cloudways panel and instead using separate webroots, specifiy the static/media paths in URL with additonal domains in Magento Admin

For e.g if you have additional domains static.yourdomain.com and media.yourdomain.com for static and media paths respectively.

First you can add them as additional domains through Cloudways Panel, this would map the additional domains/sub-domain to your application

Then in Magento panel: stores -> configuration -> web -> Base URL or Base URL Secure (in case your setup is on HTTPs) for magento 2.X, set path in following manner

static.yourdomain.com/pub/static/ (for static)
media.yourdomain.com/pub/media/ (for media)

Setting this way enables you to gain the performance, as having the additional domains/sub-domains will increase the number of parallel downloads that the browser can perform.

Hope that answer your question

To read how you can add additional domains/sub-domains please follow this KB: https://support.cloudways.com/what-is-the-difference-between-primary-domain-and-additional-domains/

Regards,
Cloudways Team

Please implement this.
In magento 2, we can insert subdomain for static and media url and use cpanel to point the the subdomain to the pub/static and pub/media folder.

Now with cloudways, we cannot do that anymore.

Agreed. This should be a thing.