Who is considered an 'Authorised signatory' for EORI application

When applying for EORI on behalf of a charity, who is considered an 'authorised signatory' please? Charity is registered with Charity Commission, and professionally audited, but not VAT registered. Trustees of large charities are generally there for expertise in the field of interest, but not up to speed with financial matters and certainly not of import control, so who else is considered acceptable, and authorised to apply, please?

Firstly an EORI is an importer/ exporter registration number to allow an entity to be recognised when making out an import or export declaration.
There is no requirement to have a VAT number to obtain an EORI but if the entity is VAT registered the EORI and VAT numbers are linked.
The EORI itself places no direct financial or reporting obligation on the entity.
There are however responsibilities for ensuring the accuracy of customs declarations even if these are made by someone else on behalf of the entity. https://www.gov.uk/guidance/due-diligence-when-making-customs-declarations I would expect as a charity you will have officially appointed trustees and usually someone specifically nominated for the finances who can apply on behalf of the charity.
Those authorised persons can also appoint someone within the organisation (in writing) to make the application on behalf of the organisation.