My brother and I just had this exact same issue this morning. We are using the Epic Games Store version of the game. We started a game a few days ago and saved it after three turns. We returned today to continue playing. I hosted it on my Intel i9 9900K system.
My brother got the spinning galaxy load screen. We rebooted the game a few times. Then I had us run the game via the Epic Launcher (launched as ADMIN). He had the spinning galaxy and after about a minute, he finally loaded into the lobby. No issues during gameplay.
I'll post again if we have any issues when we continue. We made it to turn 15 and then saved today.