TYPO3 Core

Is this related to #86734?

IMO not related

I have the same Error in the Frontend. (Version: TYPO3 9.5.9)

(1/1) #1522960188 InvalidArgumentException
Language 3 does not exist on site

Site Configuration:

rootPageId: 1
base: 'http://www.example.local'
languages:
  -
    title: Deutsch
    enabled: true
    languageId: '0'
    base: /de/
    typo3Language: de
    locale: de_CH.UTF-8
    iso-639-1: de
    navigationTitle: DE
    hreflang: de-ch
    direction: ltr
    flag: de
  -
    title: Italienisch
    enabled: true
    languageId: '3'
    base: /it/
    typo3Language: it
    locale: it_CH.UTF-8
    iso-639-1: it
    navigationTitle: IT
    hreflang: it-ch
    direction: ltr
    fallbackType: free
    fallbacks: '0'
    flag: it
  -
    title: Englisch
    enabled: true
    languageId: '1'
    base: /en/
    typo3Language: default
    locale: en_GB.UTF-8
    iso-639-1: en
    navigationTitle: EN
    hreflang: en-gb
    direction: ltr
    fallbackType: free
    fallbacks: '0'
    flag: gb
  -
    title: Französisch
    enabled: true
    languageId: '2'
    base: /fr/
    typo3Language: fr
    locale: fr_CH.UTF-8
    iso-639-1: fr
    navigationTitle: FR
    hreflang: fr-ch
    direction: ltr
    fallbackType: free
    fallbacks: '0'
    flag: fr
errorHandling: {  }
baseVariants:
  -
    base: 'http://www.example.local'
    condition: 'applicationContext == "Development"'
  -
    base: 'http://dev.example.ch.cabvs0XX.nine.ch'
    condition: 'applicationContext == "Development/Remote"'
  -
    base: 'http://example.cabvs0XX.nine.ch'
    condition: 'applicationContext == "Production"'
routes: {  }

Patch set 2 for branch 9.5 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/62859