Expected behavior

I should be able to have a radio box like this :

Actual behavior

The users are not able to set their email signature properly using optimized and properly formatted HTML. When they paste it inside there no option to not get their signature defaced by the CKEditor. Even by using javascript hack to fill the ckinstance end-up getting filtered. I can understand that you don't want to have PHP code and stuff in there, but sanitizing html markup has been something quite documented by now, we should be able to use a standard set of html markup tags, without being bothered by the editor. It should be concat with the message body. This is actually important because there no way any users want to be limited by the CKEditor for generating a signature and moving them from any others mail client such as thunderbird, it quite clear that this is a required (not optional but absolutely necessary) thing to fix this issues. Otherwise the employees prefer to continue to use desktop version of thunderbird and have the proper business image sent to customers when they send out email, not just deficient RTF signature.

Mail app

Mail app version: 1.8.2

Mailserver: Unrelated, Exim.

Server configuration

Operating system: CentOS

Web server: Apache

Database: MariaDB

PHP version: 7.4

Nextcloud Version: 20.0.7

Client configuration

Browser: Chrome, latest.
Operating system: Mac, Windows and Linux, it all the same problem.