I'm on Fedora 35 workstation (Gnome), connected through NFSv4 with fstab options "nfs4	x-systemd.automount,x-systemd.idle-timeout=300,async	0 0".

If I open a document through NFS, close it, close LibreOffice, cut the network by unplugging the Ethernet cable or turning the NFS server off, reopen LibreOffice, the latter freezes. If I reboot and open LibreOffice, it still freezes.
If I plug on the network and open LibreOffice, it works.
If I close Libreoffice, reopen it without opening a document through NFS, close LibreOffice, cut the network, reopen LibreOffice: it works. But If I then go to "Recent documents", LibreOffice freezes. If I close and reopen it, then chose recovery (of a local document), it freezes. If I close it and reopen it, choosing to discard recovery, it freezes too.

If I plug the computer to the network, go to tools → options → LibreOffice → Open Expert Configuration → org.openoffice.Office.Common → History → PickListSize, set it to 0, open a document through NFS, close LibreOffice, unplug from the network and reopen LibreOffice, it works.

There should be a short timeout (for instance 20 s: nowadays networks don't need minutes for NFS connection): the last open document, specially if it was normally closed by the user, is not essential and could be ignored, and/or removed from the "Recent documents" list, rather than blocking LibreOffice forever.