JSFiddle - React, Tailwind, and code Playground

HTML

forma
<form name="forma" method="POST" action="used-results.php" id="apliforma">
 <select class="form-control" id="main" name="make">
	<option value="">None</option>
	<option value="audi">Audi</option>
	<option value="alfa-romeo">Alfa Romeo</option>
	<option value="mercedes-benz">Mercedes</option>
</select>
and many other dropdown menus
<button type="submit" class="btn btn-primary submit" id='submit' >submit 1</button>
</form>

<br><Br>
forma2
<form name="forma2" method="POST" action="used-results.php" id="sinthetiforma">
 <select class="form-control" id="main" name="make">
	<option value="">None</option>
	<option value="audi">Audi</option>
	<option value="alfa-romeo">Alfa Romeo</option>
	<option value="mercedes-benz">Mercedes</option>
</select>
and many other dropdown menus
<button type="submit" class="btn btn-primary submit" id='submit2' >submit 2</button>
</form>

JavaScript

var jq = $.noConflict();

jq(document).ready(function (){
    validate();
    jq('select').change(validate);
});

function validate(e){
    if (e) {
        var btn = "#" + jq(this).siblings('button').attr('id');
    } else {
        var btn = ".submit";
    }
    
    
    var validation = true;
    jq('select').each(function(){ 

        if(jq(this).val().length>0)
        {
            validation = false;
        }
    });   
    
    if ( validation ) {
        jq(btn).prop('disabled', true);
  
    } else {
        jq(btn).prop('disabled', false);
    }
}