EDIT:
The pictrs migration is still taking place in the background, and there might be some problems displaying new or some old images, as well as a bit slower site performance. But it seems like the site can run well now.
The lemmy backend makes use of pict-rs for hosting images. A new version (0.5.0) was recently released, and upgrading from the previous version involves a migration that is expected to take a few hours.
I am planning to run that migration either tomorrow evening or on Saturday. If all goes well, the instance will be down for only a few hours.
Just a heads up in case you stop by and see that the site is unavailable.