Change language name based on the domain i'm on I'm looking for a solution which can alter/change a language name based on the domain I'm on.

Here I can configure one name, which is used everywhere, but can't be configured for each domain:
/admin/config/regional/language

I got a site with multiple domains. Every domain has a set of languages: en, nl and fr etc.

Each domain has different labels for those languages. For example:
domain 1: en: English
domain 2: en: International

Any suggestions?

Altering every form, every view output, just feels wrong.
You are looking for url/domain language negociation + url/path language negociation, right ?
You need both of domain+path in /admin/config/regional/language/detection/url to determine wich language to display.

I think you have to implement a new LanguageNegociation plugin in a module which do this. Have a look at :

core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php

You should be able to get your own detector (quiet looking like LanguageNegotiationUrl with both domain+path) by extending LanguageNegotiationMethodBase.