Imgur now blocks several VPNs and have issues loading embedded previews in several fediverse platforms. So instead of using imgur, you could use one of the following alternatives for uploading your images.
https://postimages.org/
https://imgbox.com/
https://imgbb.com/
https://www.imagebam.com/
On the other hand, it’s great that some instances have file size limits. It forces users to look at these image hosts instead of them just recklessly uploading images into the servers as if Lemmy is housed in a Palo Alto facility.