I was having trouble getting object storage through DigitalOcean Spaces working for Calckey and found the documentation lacking, but this thread helped point me towards the eventual correct configuration. Posting that here in case there's anyone as clueless as me in the weeks/months/years ahead, along with explanations of the different parameters:
Base URL: https://{bucket}.{region}.cdn.digitaloceanspaces.com/{bucket} (this is the base URL for images loading on your instance, it is purely for the purpose of displaying files)
Bucket: {bucket} (bucket name seems to be required, I'd get upload errors when this wasn't included)
Prefix: files (not including a prefix resulted in a // in URLs, a comment on an issue on the Codeberg repo said that the fix will be to make this field required at some point)
Endpoint: {bucket}.{region}.digitaloceanspaces.com (this is the API endpoint, for all the upload/edit/delete operations)
Region: {region} (this doesn't seem to actually be required on DO, but I included it anyway)
YMMV with other object storage providers. What tripped me up for a bit was that Calckey was storing the files with the bucket name as the top-level directory. I initially was including the Base URL as just the scheme + domain, when they were being stored in scheme + domain + bucket name. Hopefully this can be helpful to others!