That may not be a bug but a feature.
And it is not a language question, but a country case.
In US keyboard, there are 9 keys on second row, leaving large space for the return key, enough to write the label (return, done…)
In UK ( ! ), french, spanish, probably german, there are 10 keys, leaving small room for the return key. Hence the text is replace by the symbol.
That's the same for the smart keyboard (accessory).
See the difference beyween
US : https://www.apple.com/us/shop/ipad/ipad-accessories/keyboards
UK : https://www.apple.com/uk/shop/ipad/ipad-accessories/keyboards
I did not check with other languages, but I assume that's the case with any keyboard with more than 9 keys on second row.
Whatever the reason, it is, IMHO, a poor localization result.
Seems they are playing a bit with keyboards layout recently. So, that could be worth an improvement request.