@Andras Pinter Thanks for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.
S3 HD doesn't provide the indexer feature and data ingestion must use APIs that push data from source to index.
All the limits/quota increases mentioned in the public documentation are indeed possible.
However, it is highly recommended to create a support ticket if you require a quota increase beyond what is currently available.
It is crucial to keep in mind that changes to limits may be subject to various factors, including business justification.
Hope this helps, let me know if you have any further questions on this.