Created attachment 200346 [details]
Example file from Writer

Attached example file has a user field, whose text content is a hyperlink.
This is placed in the header of the document, and also inside a frame.
Next to it is a normal hyperlink.

When this is exported as PDF with PDF/A-2b enabled, and the resulting file opened in Acrobat Reader, the document is opened as RO, and only the normal hyperlink is clickable, not the one that comes from the user field.
If I remove the read-only protection from the file with the blue infobar in Acrobat, then the link from the user field also becomes clickable.

1. Open attached file
2. Export as PDF, enable the PDF/A-2b mode.
3. Open the resulting file in Acrobat Reader (with other readers like the one built into Firefox, this does not happen)
4. Notice the file opens as read only PDA/A
5. Try to click on the links
-> the ones for https://bugs.documentfoundation.org/ don't work, the normal ones for https://gerrit.libreoffice.org/ work
6. Press Enable Editing on the blue infobar of Acrobat
-> Now the links to  https://bugs.documentfoundation.org/ open in the browser

Version: 25.8.0.0.alpha0+ (X86_64) / LibreOffice Community
Build ID: 887ed47fbdb05a2cbbef5722859cdd3e7900b73c
CPU threads: 14; OS: Windows 10 X86_64 (build 19045); UI render: Skia/Raster; VCL: win
Locale: en-US (hu_HU); UI: en-US
Calc: threaded

seems to be like this since 3.3, only with PDF/A-1