Using S3 Tools

Point your tool at the endpoint from the Connect tab:

aws s3 ls --endpoint-url "$S3_ENDPOINT"
aws s3 sync ./public "s3://my-bucket" --endpoint-url "$S3_ENDPOINT"

// Node — @aws-sdk/client-s3
import { S3Client } from '@aws-sdk/client-s3';
const s3 = new S3Client({
  endpoint: process.env.S3_ENDPOINT,
  region: 'us-central-1',
  credentials: { accessKeyId: process.env.S3_ACCESS_KEY, secretAccessKey: process.env.S3_SECRET_KEY },
  forcePathStyle: true,
});

# rclone
rclone config create impulse s3 provider=Other endpoint=$S3_ENDPOINT \
  access_key_id=$S3_ACCESS_KEY secret_access_key=$S3_SECRET_KEY
rclone sync ./assets impulse:my-bucket