Hello.
I've prepared .html for Thunderbird and tried to use it in AquaMail, but one graphic didn;t worked (line on the screenshot).
I tried copy & paste it from message sent already from thunderbird.
Then i tried copy source html and paste it in AquaMail. Both method fails - AquaMail do not put images.
I attach signature HTML file used for testing, graphic used in signature, and screenshots from AquaMail.
I'm using AM v1.38.1-197 on Android 11.