Just adding this here for everyone’s reference. The current official procedure seems to be to do two sentiment polls with passing thresholds of 25k UNI and 50k UNI respectively, followed by a on-chain governance proposal.
The governance proposal requires the proposer to have 10m UNI ($260 million at today’s prices) delegated to them. Passing the vote requires 40m UNI ($1 billion at today’s prices).
https://gov.uniswap.org/t/community-governance-process/7732/1