Cleanly Monetizing my popular Windows PC software

Over the past 23 years I've been developing Zoom Player, a fairly popular media playback software for Windows PCs.

As media consumption has changed over the years towards mobile operating systems and Smart TV, Home Theater PC sales dropped and I can no longer keep my small team without considering other monetization/revenue options.

I am looking for a clean way to monetize my software. I will not bundle 3rd party add-ons or other problematic solutions that could threaten or annoy my users.

I am considering inserting advertising into dead moments (e.g. when a user pauses media playback), but I couldn't find many advertising firms that work with Windows software and those that do are an unknown to me, either sketchy looking or don't have a lot oh history to give me a sense of reliability.

I welcome any advice/recommendation you could give.

P.S.
I am willing to take on a partner if you can prove you hold the key to additional revenue.