Is there any "compatibility" type mode/option to use existing plugins with Ktor 2.0 or do they have to be migrated first? Am currently using

KGraphQL

(https://github.com/aPureBase/KGraphQL) but get following when updating to use Ktor

2.0.0-beta-1

Type mismatch.
Required:
Plugin<TypeVariable(P), TypeVariable(B), TypeVariable(F)>
Found:
GraphQL.Feature

I expect not, such a major version increment is a good moment to remove deprecated features from the codebase. I am using KGraphQL in my projects as well, however the maintainer seems to be AWOL since August/September, we might have to migrate to Graphql-Kotlin

They have to be migrated. You can try to solve your problem by renaming

ApplicationFeature

to

ApplicationPlugin

.