I’m too lazy to look, but I seem to remember hearing Solo had to make $400-$450 million to break even. The marketing costs were roughly $150 million IIRC and the movie budget was $250 million IIRC.
A quick and easy way to figure out the break even point for a movie is to double the production budget. It isn't always accurate, but it is usually close enough. The low-end estimate of Solo's budget was $250 million. So they would need, at least, $500m to reach the break even point. Could very well be much higher than that however as they effectively shot the entire movie twice and did several script rewrites.