Dear @Richard_Purkis
Unfortunately, I actually tried all three options you mentioned.
1. When using File Geodatabase format, Failed appears during the download process.
Is it because there are too many attached photos?? I think it's about more than 10GB.
2. In the case of cloning, the data source is considered as the source portal, so if there is a problem with the source portal, the cloned data will also be affected.
3. I also tried the AGO assistant. The data source is set to the source portal, and, of course, it is not available if change the source url.
Is there any other way???
Thank you for listening to my concerns during your busy time.