I have been told that NALC are to publish advice to all parish councils this week regarding donations to the Ukraine relief efforts.
We have also been told by our ALC that the current legal view is that parish councils cannot directly donate public funds to Ukraine, including Councils with the General Power of Competence, as this is sending money out of the country. (As DavetheClerk has said).
However, the General Power of Competence and section 137 can be used to provide grants to community organisations/charities to enable the hire of a village hall in order to hold a fund raising events, organize vigils, cake sales etc etc.
Chairmen / Mayors can organise a disaster fund in the community, passing the funds to some other body such as the Disasters Emergency Committee.
HTH