Brushing up on publishing my next banner ad in Adobe Animate

Hello fellow animating gurus. It's confession time and I confess: I am a bit rusty on the latest publishing techniques for banner ads.

My background: About 2 years ago, I was a publishing fool in Adobe Flash. I would publish my animation as a .swf and upload the .swf to a company that would place the ad(s) for my client. We would publish multiple versions with customizations for different cities, etc. The hosting company would then place the ads on various "appropriate" websites for customers who might be interested in the products advertised. ( home furnishings stuff ).

Ok. It was easy because all we had to do was send a .swf.

Now, however, because of the internet turning away from Flash content, I am afraid to publish a .swf. I realize that I can publish an HTML file and send that.

But, is it really as simple as that? My question is really: What file format is universally accepted and used for banner ad placement today? In other words,

if I publish HTML content, does that mean a third party hosting company will know how to publish this?

I am asking specifically, because my goal is to have my banner ad content animate on all devices. When I would publish before ( a couple years ago ) I would also publish a stationary .jpeg to use in case a device could not animate the Flash content. It would just display the .jpeg instead. That was the norm.

Please feel to ask for more clarification, if needed. I do appreciate any help and value all of your feedback.

Matt