Well the tricky part is getting them in to a single list...

But given that a SOSL query returns a list<list<sObject>> then you can easily loop through that list of lists, and add it to a flat list to display somewhere else.

Given that you want to display the sObjectType in the column as well means you could create an inline class to store a result. The class would contain two properties of sObject Label, and sObject record.

Then it's a simple matter of creating a list of that custom class and displying that list on the page block table.

Here is how mine would look:

public with sharing class TEST_soslQueryPageBlock {

    public string searchText {get;set;}
    
    public list<list<sObject>> soslResults {
        get {
            if(searchText != null && searchText != '') {
                soslResults = [FIND :searchText IN ALL FIELDS RETURNING  lead(name, email), Contact(name, email), Account(name, phone)];
            }
            return soslResults;
        }
        set;
    }
    
    public class searchResultRow{
        public string sObjectTypeName {get;set;}
        public sObject record {get;set;}
        
        public searchResultRow(sObject pObject) {
            record = pObject;
            sObjectTypeName = pObject.getSObjectType().getDescribe().getLabel();
        }
    }   
    
    public list<searchResultRow> searchResults {
        get {
            searchResults = new list<searchResultRow>();
            if(soslResults != null) {
                //Loop through the list of list of sObjects from our sosl query
                for(list<sObject> objectList : soslResults) {
                    for(sObject obj : objectList) {
                        searchResults.add(
                            new searchResultRow(obj)
                        );
                    }
                }
            }
            return searchResults;
        }
        set;
    }

}

 And this would be a simple VF page to consume it:

<apex:page controller="TEST_soslQueryPageBlock" >
Test how to put results of a sosl search in a single page block

<br/>
<apex:form >
    
    <apex:actionFunction name="af_reRenderSearchBlock" reRender="searchBlock"/>

    <apex:pageBlock id="searchBlock" >
        <apex:pageBlockButtons location="top">
            <input type="button" class="btn" value="Search" onclick="af_reRenderSearchBlock()"/>
        </apex:pageBlockButtons>
        <apex:pageBlockSection collapsible="false" columns="1">
            <apex:pageBlockSectionItem helpText="Will search multiple objects">
                <apex:outputLabel for="searchParam">Search String</apex:outputLabel>
                <apex:inputText id="searchParam" value="{!searchText}"/>
            </apex:pageBlockSectionItem>
        </apex:pageBlockSection>
        <apex:pageBlockSection collapsible="false" columns="1" title="Results" rendered="{!searchResults.size > 0}">
            <apex:repeat value="{!searchResults}" var="row">
                {!row.sObjectTypeName} - {!row.record['Name']}, 
            </apex:repeat>
        </apex:pageBlockSection>
        
    </apex:pageBlock>

</apex:form>


</apex:page>

note that I am using a repeat - but you could use a pageBlockTable.

For instances where you want to render only specific fields in a column: you can use apex:outputField and use the "rendered" parameter with something like:

rendered="{!row.sObjectTypeName == 'Account'}"