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Any HTML Experts Please Send Help

I've asked this on StackOverflow to absolutely no avail, so resorting to here.

I'm trying to create a very basic HTML email signature. I want all of the text to display in Open Sans font, which I'm importing via Google Fonts.

On Chrome it displays exactly as I want it:

However on Safari and on my IOS mobile device, Open Sans doesn't pull through:

Here's my code:
<!doctype html>
<head>
<style>
@import url('https://fonts.googleapis.com/css2?family=Open+Sans&display=swap')
</style>
</head>

<table style="
background-color: #000000;
font-family: 'Open Sans' !important;
font-weight: 400;
font-style: normal;
text-align: left;
color: #ffffff;
font-size: 14px;
line-height: 21px;
padding: 10px 40px;
border-spacing: 0;">

<tbody>

</tbody>
</table>

I imagine the issue lies in the header / table style code.

I've tried @import (as above) and also to pull in the Google Font, and I've even tried embedding the font locally as both Woff and Woff2 fonts.

Funnily enough, I have a CompSci degree, but alas I still can't do this. Any help would be massively appreciated!