Failed to bind properties under 'eureka.client.enabled' to boolean - spring-boot

Question

why is the new spring-cloud-config so complicated?
I would like to do the following: enable eureka on default and add it in some profiles (not in all).
no matter in which way I tried it, it didn't work.
I get this error Failed to bind properties under 'eureka.client.enabled' to boolean.
first way:
server:
port: 8080
eureka:
client:
enabled: false # default disabled
instance:
leaseRenewalIntervalInSeconds: 10
prefer-ip-address: false
hostname: 127.0.0.1
spring:
application:
name: app
main:
banner-mode: off
cloud:
config:
enabled: false
discovery:
enabled: true
service-id: config-server
fail-fast: true
retry:
max-attempts: 5
application:
value: app-default
---
spring:
config:
activate:
on-profile: dev
application:
value: app-dev
---
spring:
config:
activate:
on-profile: qa
import: "configserver:"
cloud:
config:
enabled: true
eureka:
client:
enabled: true # enable it in profile "qa"
serviceUrl:
defaultZone: http://127.0.0.1:8761/eureka/
application:
value: app-qa
second way:
server:
port: 8080
eureka:
client:
enabled: true # default enabled
instance:
leaseRenewalIntervalInSeconds: 10
prefer-ip-address: false
hostname: 127.0.0.1
spring:
application:
name: app
main:
banner-mode: off
cloud:
config:
enabled: false
discovery:
enabled: true
service-id: config-server
fail-fast: true
retry:
max-attempts: 5
application:
value: app-default
---
spring:
config:
activate:
on-profile: dev
eureka:
client:
enabled: false # disable in profile "dev"
application:
value: app-dev
---
spring:
config:
activate:
on-profile: qa
import: "configserver:"
cloud:
config:
enabled: true
eureka:
client:
serviceUrl:
defaultZone: http://127.0.0.1:8761/eureka/ # I also need a profile specific url
application:
value: app-qa
if I activate eureka once and never use eureka.client.enabled again, then the error with the url occurs: Failed to bind properties under 'eureka.client.serviceUrl. defaultZone' to String - but I need this profile specific url in any case!
all this has to do with the new spring-cloud-config. because after I deleted all the lines for the config-server and commented out the spring-cloud-starter-config dependency, both variants with eureka worked!
or do i have an error according to this spring-cloud-config stuff?
versions:
<spring-boot.version>2.5.2</spring-boot.version>
<spring-cloud.version>2020.0.3</spring-cloud.version>