Users of Microsoft Word can utilize the Peoplese spellcheck.  Free.

           Once configured, and a text opened in any version of MS Word, all words in the text that are not in Peoplese language will be red-lined.

           The Peoplese MS Word Spellcheck is not offered by Microsoft; it is offered by Peoplese, in the form of a  MS Word Supplementary Dictionary.  In order to use the Peoplese spellcheck, first add the Peoplese Supplementary Dictionary files to MS Word's spellcheck options.  (Steps listed farther below.)

           Note that there are two versions of Peoplese spelling:  (1) The Sound Spell Same (SSS) pure Peoplese version spells as it sounds, so when you hear a word you can spell it, and when you read a word you can pronounce it.  (2) The Alike English (AE) learner's version retains English spelling, but otherwise adopts Peoplese structure.  (You may click on the "Spelling" tab above for a thorough explanation.)  So when using Peoplese Spellcheck, you must choose either the SSS or AE version.  You also have the option of using the spellcheck of your default language, e.g. English or Swahili. You can easily switch back and forth.

Instructions for installing Peoplese SSS Dictionary on your computer:
            1. First, to download the Peoplese spellcheck files, click on this link.  Save the resulting .peoplese-spellcheck.zip file to the Download folder on your computer.  The next task is to move that zip file from your Download folder to within MS Word's spellcheck section.

            2. Open UProof, which is a directory within MS Word.  To do so, with your computer's File Explorer migrate to: 
                         C:/Users/[name of computer, often your name]/AppData/Roaming/Microsoft/UProof.
                         Copy the zip file from Downloads, paste it in UProof.
                         Right-click on ExcludeDictinoaryEN0409 -> Rename, and add prefix "ORIGINAL-" (including a hyphen). Thus the renamed file will be:  ORIGINAL-ExcludeDictionaryEN0409.  A prefix before ExcludeDictionaryEN0409 renders it non-functional; removing that prefix restores it to functionality.

            3. Now is the time to select the spellcheck in either pure Peoplese (SSS) version, or Peoplese Alike English (AE) training version recommended for Peoplese beginners. Right-click the zip file, select "Extract All", and two pairs of files (four files total)  will appear.
                                    Peoplese-AE.DIC   &   AE-ExcludeDictionaryEN0409
                                    Peoplese-SSS.DIC   &    SSS-ExcludeDictionaryEN0409            
                         Highlight those 4 files -> Copy, then move one level up to the UProof folder -> Paste.  You have transferred the zip file from Downloads to UProof, and have removed the four spellcheck files from the zip file to UProof folder.   The DIC files tell MS Word what words to accept; the Exclude files tell MS Word what to reject, i.e. what to red-line.
                         To enable the Alike English spellcheck, remove the "AE-" prefix from AE-ExcludeDictionaryEN0409. To do so, put the cursor on the file -> left click -> rename, and remove the AE and the hyphen.  Thus the pair of AE spellcheck files will be:  Peoplese-AE.DIC and ExcludeDictionaryEN0409
                         Alternately, if you want the spellcheck to inspect SSS text, delete "SSS-" from the Exclude file name, so the pair becomes Peoplese-SSS.DIC and ExcludeDictionaryEN0409.  Only one "ExcludeDictionarEN0409" is allowed without a prefix; a prefix must precede any others in the folder.
                         Now you can exit UProof.  Next, we will select a dictionary within MS Word.

            4.  Open a MS Word file (for example a file to spellcheck, a blank page).
                         From top left, click on:  File → Options → Proofing → Custom Dictionaries, which opens the small Custom Dictionaries dialog box. Click on "Add", and the contents of the UProof folder will appear.  Double-click on PEOPLESE-SSS.DIC, which will then appear on the "All Languages" list.  This is where you select which spellcheck to use.  You can follow the same procedure above to install PEOPLESE-AE.DIC,which will then appear on this "All Languages" list as a third option after Microsoft's  CUSTOM DIC. In the checkbox, check the SSS option. Open a MS Word document in pure Peoplese language, and it will  red-line all words not in the pure SSS version of Peoplese.

            Changing Dictionaries
                         To change from pure Peoplese (SSS) spellcheck to Alike English (AE) spellcheck, open UProof, add "SSS-" to ExcludeDictionaryEN0409 (which neutralizes it), remove the "AE-" prefix from AE-ExcludeDictionaryEN0409.  Then in MS Word, File -> Options -> Proofing -> Custom Dictionaries, uncheck SSS, and check AE.
                         To revert back to the original situation before installing Peoplese spellcheck, AE- and SSS- prefixes should be in place, then from ORIGINAL-ExcludeDictionaryEN0409 , remove the prefix "ORIGINAL-".  Then adjust the check boxes.

            For additional help. you may try Peoplese Community.