In Odoo 18,

In your custom module add below code, make sure in __manifest__.py file in depends 'mail' should be there
for e.g.  'depends': ['base', 'account', 'web', 'mail'],

​<?xml version="1.0" ?>
<odoo>
	​<template id="mail_notification_layout_custom" inherit_id="mail.mail_notification_layout">
    	​<!-- Force show_footer to false -->
    	​<xpath expr="//t[@t-set='show_footer']" position="replace">
        	​<t t-set="show_footer" t-value="False"/>
    	​</xpath>
	​</template>
</odoo>

Stumbled upon the same issue. Looking in the source, the best way seems to be a module, that removes the part from the hardcoded templates. 

I also found the string in many translation files, maybe that's another option to get rid of it.

Nickhil, you say that we just need to edit the templates, but, that is as a matter of facts not true.

I customised template, and it lets you only customise the "inner" text of a template, not the actual template.

It still comes in a totally ugly "white/grey" box and has a footer "powered by odoo"

The modules you suggest, are one 404, and the other not tested on enterprise, further requiring odoo 11

What do we miss?

Thanks!

Hi,

What you need to do is, enable debug mode from settings, then go to technical -> email templates.
From there select the template you want to edit and remove the code segment that has powered by Odoo.

Hope it helps