In Qt Creator: Create Project...
	Application (Qt) : Qt Widgets Application
	Build system: qmake
	default Class Information
	Translation File <none>
	Kit Selection : Desktop (Qt 6.3.0 GCC 64bit)

	Add a Push Button to default MainWindow. Attach to "clicked" slot.

mainwindow.cpp

#include "ui_mainwindow.h"
#include <QString>
#include <QFont>
#include <QFontDialog>
#include <QDebug>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_pushButton_clicked()
{
    QString fontString("Nimbus Roman,36,-1,5,700,0,0,0,0,0,0,0,0,0,0,1");
    QFont initialFont;
    initialFont.fromString(fontString);
    QFontDialog dlg;
    dlg.setCurrentFont(initialFont);
    dlg.exec();
    QString altFont = dlg.currentFont().toString();
    qDebug() << altFont;
}