Storage shows I have 24.1 GB left, but since I moved the SD card from my Samsung Galaxy 7 to S10, when I try to move an app via appmgr to SD card, I get a message that says there's not enough space. I don't want to reformat the card because I have photos on there. Any suggestions? Thanks.
Normally, not all apps are not movable to the card. Most apps actually need the 'internal' storage to run. Cards are 'external' storage. This may be your problem and not that there isn't enough room on the card.
However, did you look at actually how big the app you want to move actually is? You list what space you say the phone tells you the card has available, but you don't mention the space the app needs, even if it were movable.