The National Coalition-Building Institute does extremely effective work in reducing prejudice, resolving conflict, and welcoming diversity, based in the model of co-counselling. Most of its work is in the USA, but it has chapters around the world.
It works in two main ways: through training, and through supportive cohorts in localities and within organisations.
Their one-day Welcoming Diversity workshop is unique in the field. It starts from the premise that we all have prejudices and stereotypes that we carry around in our head, and each training begins with active permission to make mistakes in front of one another. It moves on to recognising all aspects of diversity in the room, into caucus groups around identities present in the room which feed back to the whole group, and finally practising how to make effective interventions in the moment when we see prejudice and discrimination in action.
Peppered throughout are 'speak outs' from individuals who have experienced prejudice and discrimination, giving direct insight into the impact of that. This sounds simple, but is, in my experience, an absolutely transformational aspect of the training, both for the speaker and the audience.
Their two-day Leadership training follows a similar pattern, but goes into more depth on the process involved in leading the training, in supporting individuals who are giving speak-outs, and in mediating interpersonal and intergroup conflicts. Once you have gone through the Leadership training, you gain access to annual retreats, and you are then free to develop a local chapter, to cover a geographical area, or to welcome diversity and reduce prejudice within an organisation.
As a Leader of a chapter, you also get personal support from another chapter leader to face the issues and personal button-pushing which you will inevitably experience in a leadership position.
I have been a personal fan of NCBI's work for 20 years. My one caveat with their model, though, is that it is not appropriate for everyone. That is because the speak-out process, and the support given in retreats and one to one, is based in co-counselling and thus relies on emotional catharsis. While it can be deeply healing and transformative for most people, there are people for whom it can be unhealthy, including people with unaddressed trauma, and some people who are neuro-atypical.