it should still fix some issue If I'm getting it right you're trying to filter Issue instances not by the type of the Organization they belong to, but by the Organization instances themselves, so you will have on the right a potentially very long list of Organizations to filter Issues on, but you want only CHARITies to appear in this list. This may not be the best solution if there are many Organizations, but only if they're few...
title = _('Charity')
parameter_name = 'charity'
def lookups(self, request, model_admin):
queryset = model_admin.queryset(request).filter(organisation__type='CHARITY')
def queryset(self, request, queryset):
In a Django serializer, how to set foreign key field based on view argument?