It’s not supported right now to make a specific node the raft leader. What you can do is shut down nodes 1 by 1 until you are left with voter servers among who you want your raft leader to be, it’s not really ideal. You could also try and reconfigure the cluster, but that’s also a manual operation, but I think @masnax has done some work around this.
You are likely being caught out by the rate limiting that the snap store applies to the LXD package when we do a LTS release or change the LTS package (unrelated to what you’re installing) due to capacity issues in the snap store and the large amount of updates this triggers.
And this is happening over the last couple of days due to the change of the LTS package to core20, see Weekly status #215
You might need to retry a few times.
@stgraber was discussing with snap store team whether they can prevent the rate limiting affecting manually started commands rather than periodic refreshes, but I don’t know if anything came of that.