IMPORTANT: This DOES NOT apply to Confluence Server or to Confluence Cloud pages using the Legacy Editor.
The new Confluence Cloud editor does not have a GUI control or macro to insert web images
This causes issues when dynamic images are required and need to be updated by an external source outside of Confluence.
There was an Atlassian Jira issue that should have resolved this: CONFCLOUD-65749 Ability to add Images from web in the new editor
As of October 2024, Atlassian has closed the above issue as a feature has been added to consume a web image as a local file, however, this will be a static image and will not change when the remote content is updated.
If this is what is required then please see Adding images from links now supported in Confluence
Otherwise, please keep reading.
There has been a lot of questions raised regarding this issue with no free solutions.
I wanted a definitive solution to exist on the Atlassian Community and so I prepared the following workaround:
Prepare the web image links using the following markdown format in plain text, e.g. a simple text editor, outside of Confluence:

IMPORTANT: Copy-and-pasting image links will auto-format on the page and so will preparing the markdown text directly on the page
NOTE: The ALT TEXT must have a value or the image will not render
The following is a working example using Lorem Picsum that can be copied to the page:

Verify the image is displayed on the page
After adding the web image to page, it is also possible to add a link to it by mouse hovering over the image to display the floating controls and clicking the link icon to enter a Confluence page or URL.
It is even possible to resize the image and update the position on the page from the in-line controls.
Enjoy having web images on pages again.
ADDITION: I find it ironic that the official Atlassian Community forum has the ability to add Web Images as well.
Here's a pic:
Jason Tolotta
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