After digging into this a bit more, it turns out you can use Make to do a bulk update of images using the URL from a text field.

Here's the flow:

Query all records from a specific table using a POST call to the /records/list/ endpoint.
Iterate the records, filtering only those where the \"Files and Images\" field is empty and the Image URL field is NOT empty.
Aggregate into JSON format according to the structure specified for the bulk update endpoint docs.
The format for the Files and Images field is here.
Make a PATCH call to the bulk record update endpoint using the payload created from the previous step.

That's pretty much it, uses only 4 Ops + whatever the trigger would be. For this I used a Webhook with the Table ID as a query string parameter.

I don't know how many records may be updated at a time, but it would be wise to break them up into groups and wait prior to each update so as to not exceed any limits.

Here's what you'd need:

Table (App) ID
Field Slug for the Files and Images field
Field Slug for the Image URL field

Peter Novosel - is it okay to use SmartSuite API in this manner assuming we stay within the request limits?

Import Image as URL