How to turn off text auto-completion in Gmail / Googlemail?

I don't think this is your scenario, but in case anyone else hits the same problem as I had and winds up here, Google recently added a new "Smart Compose" feature which tries to finish every word for you:

https://www.blog.google/products/gmail/subject-write-emails-faster-smart-compose-gmail/

It was intensely distracting for me, so I turned it off using

Gear > Settings > General > Smart Compose > Writing Suggestions Off

This text auto-completion, named "Input Tools" by Google can be easily turned off by using the button next to the gear icon in the upper right corner of Gmail.

Just take a look here : https://support.google.com/mail/answer/139576?hl=en

It looks like this is an update to the Google Labs Feature: "Canned Responses by Chad P"

I didn't know that Labs have auto-update enabled and did not expect such a functionality from this add-in.

After disabling all Labs with https://mail.google.com/mail/u/0/?labs=0 and confirming that the completion was gone, I enabled them one by one to find the culprit.