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.

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?