General
First let's have a look at general adjective nominalisation rules - something similar happens with colours:
a) Das Blau des Himmels ist heute wieder wunderschön.
Ich spiele begeistert Roulette, meistens setze ich auf Rot.
vs.
b) Ich habe mir viele Autos angeschaut, am Schluß habe ich mich ins Blaue hinein für das Blaue hier entschieden.
Ich habe mich in den Finger geschnitten, ich glaube das Rote, was da rauskommt, ist Blut
Case a) has a noun "das Blau"/ "Rot" that denotes nothing but the state of being of that colour, it's a nominalized and generalized attribute describing exclusively the state of being blue, ignoring any other aspects.
The a) nominalisation is only possible for some specific types of adjectives: colours, languages, and some selected other ones like "Fett, Recht, Tief, Hoch, Dunkel, Heil, Leid und Wild".
Case b) has similar nouns, the only difference being that whatever we're talking about has (can have) many more characteristics than just being of that colour - we're making it clear that we know and accept there's many more aspects of the thing.
The b) nominalisation is a general mechanism in German an can be applied to basically any adjective.
Applied to Language
Now let's transform that into languages:
a) Mein Deutsch ist wesentlich besser geworden.
b) Das Deutsche in uns kommt immer dann zum Vorschein, wenn wir im Urlaub ein Handtuch und eine Liege zur Verfügung haben.
The a) nominalisation form will always refer to language, no exceptions possible, while the b) nominalisation may refer to language, but also, like in the above example, to cultural aspects other than the language.
So, strictly speaking, when you translate something "in/nach/auf Deutsch" you're simply changing the language (probably what Google Translate or DeepL do). If you translate "ins Deutsche" you might cover other aspects like cultural background, or even change the whole structure of the text completely for example when translating poems. You could say you can translate a technical text "auf Deutsch", but probably not a poem or song lyrics (because you typically need to consider more aspects there than just the language)
There are many more subtile differences between the two nominalisation types, but the above is the most important one. There's an in-depth essay on the penomenon here, in case you want to dig deeper.