Sharing scribbles via Nextcloud ?

I've just installed xournal++ on both a GNU/Linux system and an Android mobile. Wrote something "on" a PDF on the PC and synchronized the directory containing the PDF and the .xopp file via NextCloud on my cloud, from which I synchronized them both to the Android mobile.

Now, the xournal_mobile on Android gives me 2 options:

• Open, which only lets me me pick files from "Other Apps" (but no NextCloud among them)
• Import PDF, which lets me open a file from NextCloud but won't let me pick the .xopp file, only the .pdf file

Is there a way I'm missing to read notes written on the PC from the Android app ?