https://github.com/IndexBraille/linux-driver/pull/10

commit 52c02197ba7f03dccf7bbaa8dd789dce2740e785
Author: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date:   Sun Oct 30 15:27:42 2022 +0100

    Avoid detecting all txt files as application/x-idx-doc
    
    All .txt files were previously detected as application/x-idx-doc MIME
    type, thus basically breaking printing them.
    
    Whitespaces in MIME files mean OR. We need to use + to make it AND,
    so that only .txt files that have the 1b44 marker get recognized as
    application/x-idx-doc.

diff --git a/mime/indexbraille.types b/mime/indexbraille.types
index 90de018..dca2c68 100644
--- a/mime/indexbraille.types
+++ b/mime/indexbraille.types
@@ -1,6 +1,6 @@
 ################################################################################
 # Index Braille MIME-types handled by the printer.
-application/x-idx-doc	txt string(0,<1b44>)
+application/x-idx-doc	txt + string(0,<1b44>)
 application/x-idx-fw	ibe string(0,<1b74>)
 
 ################################################################################
