Euro-Office is a fork of OnlyOffice, which has questionable Russian ties. This is explicitly part of the reason for doing a hard fork:

• ONLYOFFICE is a Russian company (despite many attempts to hide this), and nearly all developers reside in Russia. Open Source is a global effort, but current political situation makes collaboration hard and trust difficult to earn. Especially when development is not transparent and open. A lot of users and customers require software that is not potentially influenced or controlled by the Russian government.

In general it’s worth reading their github readme. They’re very open about where they get their support from and what their priorities are, and they also explicitly address their relationship with LibreOffice.