Euro-Office does not currently provide full support for ODF; see https://nextcloud.com/blog/euro-office-building-momentum
"Euro-Office roadmap: Security, performance, and ODF support"
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Improve ODF support"
"One item we want to call out specifically: #EuroOffice will work towards full #ODF support. That is not only because it matters technically, but also reflects our priorities: a focus on open standards."