Related question: what's the mechanism to wait for everything to resolve? Calling await doesn't seem to do much.

let vpcNameToId: { [index: string]: any } = {};
for (let vpc of vpcList) {
    // create a lookup table
    const vpcName = vpc.tags.apply(v => v?.Name ?? null);
    const vpcId = vpc.id;
    pulumi.all([vpcName, vpcId]).apply(([name, id]) => {
        vpcNameToId[name] = id;
    });
}

console.log("" + Object.keys(vpcNameToId).length);

Here the console output is zero items.

Is there an equivalent to Promise.resolve for apply()?

As I puzzle through this, I end up with "apply" inside "apply" statements just to ensure everything is resolved.

This should not be the case in general - though depends a bit on specific code you are trying to write.

See https://www.pulumi.com/docs/intro/concepts/programming-model/#frominput as well (and that whole section more generally).

Get the string from an Output<string>

I'm finding I have to call pulumi.all(variable).apply()

It turns out the issue was that array objects don't play well with standard array objects. For example, an Input<RouteTableRoute> object cannot be used with syntax like "[...myObj, ...anotherObj]" when defining routes in aws.ec2.RouteTable. I had to call apply(v => v.forEach(e => someVar.push(e))). It would be awesome to have some additional documentation around this.