Standing Conference on Russian Borders
Given that Russia has the longest border of any country in the world, and has been invaded many times, and that Putin believes that the expansion of NATO and the EU is a threat to Russia and was a contributory cause to his invasion of Ukraine in 2022, and given that secessionary or separatist sentiment is one of the most frequent causes of modern wars, a standing conference on Russian borders might be an idea worthy of consideration.
Meeting regularly, perhaps twice a year, and more frequently if events demanded it, the conference would discuss events and air concerns and disagreements. Treatment of Russian minorities in non-Russian states would be frequently on the agenda.
The Standing Conference would be under the aegis of the United Nations, with a neutral facilitator.

