When you rotate an image in your phone or on your computer (by right-clicking or going into the image options and selecting "Rotate Right" or w/e), the device is not editing the image to rotate it 90 degrees. It's just adding a little metadata tag that tells devices loading the image "display this, but rotate it 90 degrees".
Lemmy scrapes off metadata as a privacy concern, since this also holds personal and location data. There have been a few medium-profile events of internet stalkers getting location data off of women's selfies and going straight to their homes.
I'm not sure if there's a simpler solution, but opening the image in an image editor and saving it again should remove the metadata tag and save it as an actual, upright image. However, this is a problem that the devs should fix - platforms like Discord also shave off metadata, but know enough to leave the orientation data intact.
I think the best we can hope for in the long-term is an email-like adoption.
Individuals self-hosting major servers on donation money is not sustainable. This sucks for the people for whom this is "what Lemmy is", but it's the truth. There will come a time when Lemmy-at-large gets so big that Lemmy.world has to close (or de-federate), as users and content will outgrow voluntary revenue.
What we can hope for is that Lemmy is not taken over by one huge corporate instance, but instead 3-4 competing, inter-federated corporate instances. A Meta instance, a Google instance, and a Bytedance instance, for example. In addition to these, smaller (non-social-media) companies and institutions (game companies, universities, political organizations, etc.) would run their own Lemmy instances for the benefit of their members and users.