btcpayserver/BTCPayServer/Views/UIAccount/LoginWithLNURLAuth.cshtml

@model LoginWithLNURLAuthViewModel
@{
    Dictionary<string, string> formats = new Dictionary<string, string>()
    {
        { "Bech32", LNURL.LNURL.EncodeUri(Model.LNURLEndpoint, "login", true).ToString().ToUpperInvariant() },
        { "URI", LNURL.LNURL.EncodeUri(Model.LNURLEndpoint, "login", true).ToString().ToUpperInvariant() }
    };
}

<div id="lnurlauth-section" class="twoFaBox">
    <form id="authform" asp-action="LoginWithLNURLAuth" method="post" asp-route-returnUrl="@ViewData["ReturnUrl"]">
        <input type="hidden" asp-for="LNURLEndpoint"/>
        <input type="hidden" asp-for="UserId"/>
    </form>
    <h2 class="h3 mb-3">LNURL Auth</h2>
    <div class="align-items-center">
        <ul class="nav justify-content-center my-2">
            @for (int i = 0; i < formats.Count; i++)
            {
                var mode = formats.ElementAt(i);
                <li class="nav-item">
                    <a class="btcpay-pill @(i == 0 ? "active" : "")"
                       data-bs-toggle="tab" data-bs-target="#@mode.Key" role="tab"
                       href="#">
                        @mode.Key
                    </a>
                </li>
            }
        </ul>
        <div class="tab-content">
            @for (int i = 0; i < formats.Count; i++)
            {
                var mode = formats.ElementAt(i);
                <div class="tab-pane text-center @(i == 0 ? "active" : "")" id="@mode.Key" role="tabpanel">
                    <div class="qr-container" style="min-height: 256px;">
                        <vc:qr-code data="@mode.Value"></vc:qr-code>
                    </div>
                    <a href="@mode.Value" class="btn btn-primary mt-3" rel="noreferrer noopener">
                        Open in wallet
                    </a>
                </div>
            }
        </div>
        <p>Scan the QR code with your lightning wallet and link to your user account.</p>
    </div>
</div>

<script>
    function check() {
        const request = new XMLHttpRequest();
        request.onload  = function() {
          if (request.readyState === 4 && request.status === 200) {
            setTimeout(check, 1000);
          } else if (request.readyState === 4 ){
              document.getElementById("authform").submit();
          }
        }
        request.open("GET", @Safe.Json(Url.Action("LoginCheck", "UILNURLAuth", new { userId = Model.UserId })), true);
        request.send(new FormData());
    }
    check();
</script>