How to insert HTML signature in emails in Gmail?

Question

gmail

It is required to install an HTML signature in a letter in gmail. The standard signature editor is not suitable, as it has limited functionality.
We made a separate HTML for the signature. Copy-paste was inserted into the built-in editor (they copied the layout, not HTML, since you cannot paste HTML into the editor).
On desktops - everything is fine, but on mobiles, adaptive, of course, does not work, since adaptive styles do not cling to copy-paste.
Are there any solutions?

Answer 1

https://support.google.com
This is the Google Help Center, in English or Russian, find Gmail, enter a query in the search box, try to find the answer there in both languages.
Language selection button - at the bottom left of the Gmail support page

Answer 2

Use not the Gmail web interface, but a third-party mail client with the ability to fully control the HTML code of the letter or send it by script (for example, in PHP) using the credentials of the Gmail account.