Tkabber

ispell/aspell unfortunately don't allow to use more than languages than one when doing spell check.

Application is able to work around this limitation of course.

Here is enhancement request for tkabber to allow using multiple languages at once (like en and pl) when doing spellcheck.

Appears that not only ispell/aspell can be used in Tkabber's
Ispell plugin but also hunspell. It supports specifying multiple
dictionaries, so the following options work for me (for example)
with both English and Russian at the same time:

set ::plugins::ispell::options(executable) /usr/bin/hunspell
set ::plugins::ispell::options(command_line) "-d ru_RU,en_US"
set ::plugins::ispell::options(dictionary_encoding) ""

So, I'm closing this bugreport.