It seems I cannot open with Neovim the files I have encrypted with Vim. Neovim just open the files without decrypting them, displaying all those gibberish character sequence.
Is it considered normal ? Is there a way around, or is it a bug ?
All support for
cryptmethod was removed in
85338fe. See the linked pull requests for (lengthy) discussions about it. There is no way to open these files with Neovim. You will need to use Vim.