How to put checkmarks on a checklist in Google Docs
As you know, the checkmark bullet list is not available on Google Docs's Android version.
A not elegant workaround is to insert the checkmark character yourself then realign it.

Use one of the many keyboard apps that provide unicode characters (I used this). Search for checkmark, copy and then paste it on your document. Then realign it to be on the same column than the real bullets as shown on the image.

Disclaimer: I am just a use of the linked app.