How to check Firefox/Chrome developer console/tools on Android without a computer?
That feature seems to be unavailable for all major android browsers.
You could try Opera-mini instead.

Reset the console output by opening a new tab with the address debug:resetconsole

Open a tab on the page on which you want to do the inspection:

Run JavaScript code on the page by replacing the address in the address bar with the following address javascript:var%20n%3Ddocument.firstChild%3Bwhile%28n%20%26%26%20n.nodeType%21%3DNode.ELEMENT_NODE%29%20n%3Dn.nextSibling%3Bconsole.log%28n.outerHTML%29%3B
Retrieve the output by opening a new tab with the address debug:console