https://www.epo.org/en/node/interpretation-oral-1

Can I use non-official languages during oral proceedings in opposition held by VICO?

You may use one of the official languages of the EPC contracting states other than English, French or German on condition that you make provision for interpreting into the language of the proceedings. This means that you have to make arrangements for interpretation. On request, the EPO will set up extra audio channels for simultaneous interpreting in Zoom. The request should be submitted at least one month before the date of the oral proceedings (i.e. the time limit under Rule 4(1) EPC).

Please make sure that your interpreter connects to the oral proceedings at least 15 minutes in advance so that the extra audio channel can be set up before the oral proceedings start.

Since the provision of extra audio channels is a courtesy service, no rights can be derived from their non-availability during oral proceedings (e.g. due to technical problems). In such cases, the division will allow time for consecutive interpreting.