I see that `legacy` means `P2PKH` in both command line options and RPC help info:
```
-addresstype
What type of addresses to use ("legacy", "p2sh-segwit", or "bech32", default: "p2sh-segwit") 
```
```
getnewaddress ( "label" "address_type" )
...
2. address_type    (string, optional, default=set by -addresstype) The address type to use. Options are "legacy", "p2sh-segwit", and "bech32".
...
```

The useLegacyAddress checkbox describes itself as “Generate legacy address” - however, it actually makes the wallet GUI generate “p2sh-segwit” address for the user if it's checked.
QAction *copyLabelAction = new QAction(tr("Copy label"), this);
    QAction *copyMessageAction = new QAction(tr("Copy message"), this);
    QAction *copyAmountAction = new QAction(tr("Copy amount"), this);
    
    contextMenu = new QMenu(this);
    contextMenu->addAction(copyURIAction);
    contextMenu->addAction(copyLabelAction);
    contextMenu->addAction(copyMessageAction);
    contextMenu->addAction(copyAmountAction);
    
    connect(ui->recentRequestsView, &QWidget::customContextMenuRequested, this, &ReceiveCoinsDialog::showMenu);
    connect(copyURIAction, &QAction::triggered, this, &ReceiveCoinsDialog::copyURI);
    connect(copyLabelAction, &QAction::triggered, this, &ReceiveCoinsDialog::copyLabel);
    connect(copyMessageAction, &QAction::triggered, this, &ReceiveCoinsDialog::copyMessage);
    connect(copyAmountAction, &QAction::triggered, this, &ReceiveCoinsDialog::copyAmount);
    connect(ui->clearButton, &QPushButton::clicked, this, &ReceiveCoinsDialog::clear);
}
void ReceiveCoinsDialog::setModel(WalletModel *_model)
{
    this->model = _model;
    if(_model && _model->getOptionsModel())
    {
        _model->getRecentRequestsTableModel()->sort(RecentRequestsTableModel::Date, Qt::DescendingOrder);
        connect(_model->getOptionsModel(), &OptionsModel::displayUnitChanged, this, &ReceiveCoinsDialog::updateDisplayUnit);
        updateDisplayUnit();
        QTableView* tableView = ui->recentRequestsView;
        tableView->verticalHeader()->hide();
        tableView->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
        tableView->setModel(_model->getRecentRequestsTableModel());
        tableView->setAlternatingRowColors(true);