Put simply, the word ‘gospel’ means ‘Good News’, but of what? Many writers on this subject tend to speak about Christ and His life, death, and resurrection, as the linked articles expound, but there’s a lot more to this story. The first article expands the story further, with some handy links including the following- “What do we know about Christ - from non-biblical sources?”
http://www.provethebible.net/T2-Divin/D-0201.htm
Much of the time when Christ used the term ‘gospel’ it was in connection to the “Kingdom of GOD” or “Heaven” which is still to come to Earth in fullness. It’s certainly ‘Good News’ for most of Earth’s inhabitants, especially with all the bad news we’ve had lately, which doesn’t seem to be improving. Unfortunately, we seem destined to learn the hard way that we cannot rule ourselves. We need GOD to be in charge. He made us, He knows best. GOD is the only one who truly cares for our future welfare.
The coming Kingdom of GOD will be nothing like this current corrupt Matrix. No one has heard, seen, or imagined what GOD has designed for those who love Him. 1 Corinthians 2:9
Eventually, after the Millennium, the New City of GOD comes down to “the New Earth”, and it’s a massive cube, 1,400 miles, or 2,200Km long, wide, and high. Revelation 21:16-17 Do some calcs on how many 5-acre apartments you could fit in this massive City. It gives new meaning to what Christ said about there being "many rooms" in His Father's House. It really is ‘good news’.
https://biblical-christianity.com/what-is-the-gospel-of-jesus-christ
https://www.executableoutlines.com/top/gospel2.htm
https://www.ucg.org/bible-study-tools/booklets/the-gospel-of-the-kingdom