Hi, I am looking forward to why sidenav do not work properly. I would like to tell you one practical issue for some combination of developer tools.

If I use multiple lines for define button (other code is not important for this issue):

<button
                        class="navbar-toggler text-white" 
                        data-mdb-collapse-init 
                        type="button"
                        data-mdb-target="#sidebarMenu"
                        aria-controls="sidebarMenu"
                        aria-expanded="false"
                >

When template system Smarty do trimwhitespaces to remove white spaces, it will be:

It is because of data attribute without value. It will be merged to one data-mdb-collapse-inittype="button"

Solution: data-mdb-collapse-init=""

Or do not split button attributes to several lines. I am not sure what exactly works bad, but attribute without value can be problem. So just information for you.