luci-app-btcpayserver/luasrc/view/btcpayserver/status.htm

<%
local util  = require "luci.util"
local container_status = util.trim(util.exec("/usr/libexec/apps/btcpayserver/btcpayserver.sh status"))
local container_running = string.match(string.lower(container_status), "^up .* (seconds|minutes|hours)")
-%>

<div class="cbi-value">
    <label class="cbi-value-title">Status</label>
    <div class="cbi-value-field">
        <% if container_running then %>
            <button class="cbi-button cbi-button-success" disabled="true"><%= container_status %></button>
        <% else %>
            <button class="cbi-button cbi-button-negative" disabled="true"><%= container_status %></button>
        <% end %>
    </div>
</div>

<%
if container_running then
    local port = util.trim(util.exec("/usr/libexec/apps/btcpayserver/btcpayserver.sh port"))
    if port == "" then
        port = "3000"
    end
-%>
<div class="cbi-value cbi-value-last">
    <label class="cbi-value-title">&nbsp;</label>
    <div class="cbi-value-field">
        <input type="button" class="btn cbi-button cbi-button-apply" name="start" value="<%:Open btcpayserver%>" onclick="window.open('http://'+location.hostname+':<%=port%>/', '_blank')">
    </div>
</div>
<% end %>