Options

1. Static approach - we create a temporary feature flag for allowing a different default skin for anonymous users. Using this we'd update configuration to give anonymous users Vector 22 and logged in Vector [T891925]

Pros: Should be a relatively quick solution
Cons: Adds technical debt to MediaWiki core. We'd need to commit to removing that code at some future date. People who want Vector 22 will lose Vector 22.
Story size: Large

2. Dynamic: T321527

Pros: A useful capability that would allow us in future to roll out different preference defaults to anonymous users/logged in users and temporary users (think feature management)
Cons: High effort, involving multiple teams. People who want Vector 22 will lose Vector 22.
Story size: XL

3. DB Script: We run a script to migrate users using the Vector 22 skin - T300919#8650623

Pros: No work required
Cons: Possibly blocked by DBAs (but perhaps possible if we're able to stagger the database updates); People who want Vector 22 will lose Vector 22.
Story size: M (if we can work through the database options)

4. UI: T331070

Pros: Web-team don't need to involve any other teams (except to run sampling by DBA); Nobody loses their skin if they don't want to.
Cons: Requires design input; Worse case: Adds a temporary preference row for all active users.
Story size: M.