Use subdomain from third-party provider for A-record to load balancer

Hello.

In the case of a third-party domain provider, I think the A record needs to register the IP address.
In other words, I don't think it is possible to register the ALB DNS name as is as an A record.
Unlike Route53, there is no alias record, so if you want to use the ALB DNS name as is, you will need to register it with a CNAME record.
https://www.hosteurope.de/faq/domains/verwaltung/nameserver-eintraege/