A few years ago, audio in and out uses 3.5mm jack. However, technology change rapidly and at some point your existing speaker system become obsolete.
And it is really frustating right? Worry no more, I made a few guide on how to convert digital audio out to an anlanog 3.5mm jack input.
Please feel free to follow this link: http://www.skyworthphilippines.com/2019/05/how-to-connect-skyworth-led-tv-and.html
Hope it will help you! Good luck...