I have had this problem with Brave in the past, and it has now returned to haunt me.
With DuckDuckGo as my search engine, every search I enter has “ed” appended in the DuckDuckGo page and search bar that DDG presents.
For example, if I enter the two words
incremental improvement
in the search bar, the DDG results page presents me with a search term of
incremental improvemented
and the original (Brave) search bar displays duckduckgo.com/?q=incremental+improvemented&ia=web
I started using Safari for a while, some months ago, and I have been back with Brave for a few weeks, and now it has suddenly recurred.
This problem does not occur with DDG in a Chrome window.
I cannot change my private default search engine from DDG to Brave.
What I have found useful is when opening Brave and typing in the search engine I am shown 2 icons, Brave and DDG, I click on Brave ‘of course’.
If I click on Brave I get results from Brave, if I click on DDG I get results from DDG. I have uploaded the image.
Now, that we made sure the newly-added instance of DuckDuckGo works properly, you could remove the old instance, and edit the new instance’s details however you like.