The "learn more" link tells you that you can still download your data. I'm not sure how. Website maybe? Because the app only has "learn more" and "close app" as options. Interestingly the fyp still loads and you see a video in the background.
I do think it'll come back this week but it's not clear what the legal mechanism is. Since the ban has gone into effect the extension in the law doesn't seem to apply anymore. This would then seem to require Congressional action and there doesn't seem to be much appetite for that but maybe that's because Republicans in Congress want to give credit for saving Tiktok to Trump when he becomes president on Monday.
Another option being talked about is nonenforcement by the Department of Justice. Some dismiss this by saying "the DoJ can change their mind" but that's not strictly true. Defendants in a case can rely on statements by prosecutors. It's a valid defense. If the Attorney-General makes an official statement saying "we will not prosecute Amazon or Google or Tiktok for 90 days (or whatever) while we work this out", that's absolutely a legal defense should the DoJ ever change their mind.
Basically, this is now a shakedown as some Trump allies will seek forcibly buy Tiktok or at least a large stake in it as a price for its continued operation in the US. It's unclear if Tiktok will acquiesce to this.
Remember though, Bytedance has significant US investors so there are conflicting forces at play here.
As soon as I try to login to my US account it bricks the app.
YMMV.
[0] - https://www.404media.co/candy-crush-tinder-myfitnesspal-see-...