I tried Aluigi's dune2.bms but it returns this error:

dune2.bms:

QuickBMS generic files extractor and reimporter 0.12.0
by Luigi Auriemma
e-mail: [email protected]
web:    aluigi.org
        (Aug 24 2022 - 10:55:28)
                          quickbms.com  Homepage
                            zenhax.com  ZenHAX Forum
                     @zenhax @quickbms  Twitter & Scripts
- GUI mode activated, remember that the tool works also from command-line
  where are available various options like folder scanning, filters and so on
- select BMS script. type ? for using the content of clipboard like a script
- select input archives/files, type * for the whole folder and subfolders
- select output folder where extracting files
- open input file C:\Westwood\RA2\ra2.mix
- open script C:\Users\asd\Desktop\New folder (3)\dune2.bms
- set output folder C:\Users\asd\Desktop\New folder (3)\RA2
  offset   filesize   filename
--------------------------------------
  00030000 1114126    z҅,@Ö#f_K5��ڻeK'X
- it's not possible to create that file due to its filename or related
  incompatibilities (for example already exists a folder with that name), so
  now you must choose a new filename for saving it.
  if you press ENTER a new name will be generated automatically.
  - old: z҅,@Ö#f_K5��ڻeK'X
  - new:
  0014000e 267124722  [

mix1.bms:

QuickBMS generic files extractor and reimporter 0.12.0
by Luigi Auriemma
e-mail: [email protected]
web:    aluigi.org
        (Aug 24 2022 - 10:55:28)
                          quickbms.com  Homepage
                            zenhax.com  ZenHAX Forum
                     @zenhax @quickbms  Twitter & Scripts
- GUI mode activated, remember that the tool works also from command-line
  where are available various options like folder scanning, filters and so on
- select BMS script. type ? for using the content of clipboard like a script
- select input archives/files, type * for the whole folder and subfolders
- select output folder where extracting files
- open input file C:\Westwood\RA2\ra2.mix
- open script C:\Users\asd\Desktop\New folder (3)\mix1.bms
- set output folder C:\Users\asd\Desktop\New folder (3)\RA2
  offset   filesize   filename
--------------------------------------
- signature of 4 bytes at offset 0x00000000 doesn't match the one
  expected by the script:
  this one: ""
  00 00 03 00                                       ....
  expected: "MIX1"
  4d 49 58 31                                       MIX1
- 0 files found in 0 seconds
  coverage file 0     0%   4          281888480  . offset 00000004
Press ENTER or close the window to quit

I'm looking for existing tools to unpack Red Alert 2 .mix with filenames. It shares the same format as previous Command & Conquer games.

redalert2_mix.rar

Both those MIX files are encrypted with Blowfish encryption - details at https://web.archive.org/web/20050313035137/http://xccu.sourceforge.net/documents/mix_Format.html

There are tools out there to read the MIX archives - eg some here perhaps: https://modenc.renegadeprojects.com/MIX such as XCC Mixer from https://xhp.xwis.net/

Added support https://github.com/smiRaphi/UniPyX/commit/4e30da708bcdb3929e92bc6a86ac9a5173a1bef7

4 hours ago, wattostudios said:

Both those MIX files are encrypted with Blowfish encryption

And small correction/addition: the Blowfish key is encrypted with RSA and it uses big endian Blowfish in mode ECB