Your backing is primarily voluntary funding for people or initiatives, not a donation in the tax sense. Whether you can deduct your contribution from your taxes depends on the status of the relevant Community – for example, whether it is run by a tax-exempt association.
If the Community initiator you back is tax-exempt, you may, in some circumstances, be able to deduct your contribution from your taxes. To do so, you need a donation receipt confirming tax deductibility, which the Community initiator can issue on request.