For nav we don't need the complete CSS/JS and to avoid breaking webapps (bugs/blog/forums/etc) we add it in a class.
For the CSS, we include only require bootstrap class to the nav, and we add them within the ".mganav" class, see mga-bootstrap.scss
For the JS we only need the collapse, this help to minify it.

This is to help to generate these two files.

install npm: 
urpmi npm

Download source on https://github.com/twbs/bootstrap/archive/v4.6.0.zip 

cd bootstrap-4.6.0/
mkdir mga

install local dependencies: 
npm install

add mga-bootstrap.scss in scss/

Add on package.json:
    "mga": "npm-run-all css js mga-*",
    "mga-js": "terser js/dist/util.js js/dist/collapse.js --compress typeofs=false --mangle --output mga/bootstrap.min.js",
    "mga-css": "cleancss -O1 --format breakWith=lf --output mga/bootstrap.min.css dist/css/mga-bootstrap.css",

run everything:
npm run mga

the file are on mga/