User uploading logo with no transparency

I am currently designing a registration journey where non tech-savvy users can build their own website.

In one of the steps, users will have to upload their logo that will be displayed in the top-left corner of both their customer facing website (above a full screen image) and in their dashboard (on a white nav bar).

Target users will have their own brand/logo, but are likely to not be acquainted with the idea of file types (JPEG, PNG, SVG) and transparent background, the latter being the ideal choice -the logo will be placed on an image.

enter image description here

The visual design cannot be changed.

There is the possibility that people will upload JPEGs with visible background. This doesn't present a usability issue, but definitely ruins the overall experience and does not produce a "professional" output.

Websites like WIX don't even deal with the problem ("Upload a PNG", they say).

What are best practice in a scenario like this? 1) allowing them to upload any type of logo, and slightly ruining the overall result? (bare in mind, this will be their website, and guaranteeing them a professional output is a fundamental part of the experience) 2) recommending to upload a PNG; if not possible, advising them to skip and later, after getting their hands on a PNG or SVG, uploading it? (this would break the flow) 3) Other solution?