My suggestion is to enter the text already encoded as UTF-8 and then to instruct
vim to accept other than, or additional languages to English for the spell check.
With the following example containing two intentional errors:
Kiti didieji miestai: Kaunas, Klaipėda, Šiauliai, Panevėžys.
This is correct, but here is an errror
L'école se situe en face de l'hôtel Bienvennu
the default correction by
set spell is the following
This may be changed, e.g. to check only for French by
:set spell spelllang=fr:
or to check simultaneously for multiple languages. Altogether with Lithuanian, the command here is
:set spell spelllang=lt,fr,en. Note the list is without a blank after the comma:
This is how to add new dictionaries to the checker: As an example, for Spanish, call
set spell spelllang=es. This opens a dialogue to fetch the corresponding
wget to be stored in the path of
.vim/spell. There are languages with multiple definitions, e.g. British English / US English.