There exist unit tests for the feature "Data Provider". But they do not work, if you do it manually by the dialog.

The test is
https://opengrok.libreoffice.org/xref/core/sc/qa/unit/dataproviders_test.cxx

The test files are
https://opengrok.libreoffice.org/xref/core/sc/qa/unit/data/dataprovider/html/test1.html
https://opengrok.libreoffice.org/xref/core/sc/qa/unit/data/dataprovider/xml/test1.xml
Download them, the opengrok page has a blue "Download" item.

For the case testHTMLImport:
1. Open a new spreadsheet.
2. Define a database range "testDB" for the range A1:K11. That is menu Data > Define Range
3. Start Data Provider dialog. That is menu Data > Data Provider.
4. Select "TestDB" from down-load list `Database Range`
5. Select "HTML" from down-load list `Data Format`
6. Click on `Browse` button and find the downloaded file "test1.html".
7. Click on `Apply` button. Error: No import in Preview.
8. Click on `OK` button. Error: No data imported.
BTW, the import via menu Sheet > External Links works. Use locale English(USA) and detect special numbers.


For the case testXMLImport:
1.-4. see above
5. Select "XML" form down-load list `Data Format`
6. Click on `Browse` button and find the downloaded file "test1.xml".
7. 8. see above.
The test sets "maFieldPaths". There is nothing corresponding in the dialog.
BTW, the import via menu Data > XML Source works. Use the recurring element //book and link it to cell A1, for example.


As the tests themselves do not fail, I guess that there is something wrong with the dialog.