Xsel fails with Zotero PDF viewer

[Jopp-gh]

In Zotero, a pretty popular and useful bibliography software, xsel is unable to get selected text in PDF / epub documents.

A workaround is to use xdotool to force copy text with "Ctrl+c" (no critique to xdotool, but I prefer xsel to copy text selections)

Example
xsel -bc
Should put data to the clipboard. But it doesn't get text selections in the default PDF viewer of Zotero. Zotero uses a PDF viewer to load PDFs but this plugin seems to ignore x11 selections.

However, xsel works on strings in Zotero's side panels (by default on the right hand side). So the fault is to search in the PDF plugin that Zotero ships by default.

Could you please check this issue? since the PDF viewer isn't their own plugin the developers of Zotero are most probably not involved and therefore, unable and interested to investigate this bug.

Os: Linux mint 21 Cinn. (Ubuntu based)
Wm: muffin
Xsel v.1.2
Zotero v.7.0.11