Helm - UPGRADE FAILED: cannot patch "..." with kind Deployment: Deployment.apps

I was running the older 2.16.0 version of ChartMuseum Helm Chart. I am trying to update it to use newer 3.1.0. When I try to upgrade using helm upgrade -n , the upgrade fails with the following error:

Error: UPGRADE FAILED: cannot patch "..." with kind Deployment: Deployment.apps "..." is invalid: spec.selector: Invalid value: v1.LabelSelector{MatchLabels:map[string]string{"app.kubernetes.io/instance":"chart-rep", "app.kubernetes.io/name":"chartmuseum"}, MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable

I am not sure but I believe this is because of helm v3? I was going through [this][3] page where I found helm v3 is a prerequisite.
The change from 2.16.0 to 3.1.0 requires helm v3.

I also have a pv bound to older version and ideally I want it to bind to the newer one.I am also using rolling-update strategy.

What steps do I need to take so that the upgrade works?

This is not a Helm issue. You are probably trying to update the LabelSelector fields which are immutable. This is expected behaviour as per the kubernetes.

StackExchange DevOps Q#14127, answer score: 3