In increasing order of casualness I recommend: Elite Dangerous->X3/X4->Everspace/Everspace 2-> No Man’s Sky.

Everspace 2 is a spiritual successor to Freelancer, so probably your best bet ( Everspace 1 is more roguelike, but holds up nicely ). Speaking of Freelancer, I hear the game is still alive and has a vibrant community around it.

If you ever want to revisit Elite shoot me a message, I may help you with starting up. They say Elite doesn’t have a learning curve but a cliff, so help is usually needed. Luckily the game has the most welcoming and helpful community I’ve seen in/around a video game.

Other than these, there’s Chorus, but I haven’t played that one and it seems more story driven than open-ended.