A new free-software forge: sr.ht

It may be because, as in my case, you have a photo UID on the key. This can be many kilobytes; in my case it results in a key more than 600 KiB. You can temporarily delete photo UIDs and export it, and then refresh your key from a keyserver to get your UIDs and their signatures back. After all, encrypting email to you doesn't need photos anyway. For some unknown reason, '--export-options export-minimal' doesn't remove photos.

$ gpg --edit-key ...
(gpg) uid 3
(gpg) deluid
(gpg) save
$ gpg --export ...
$ gpg --refresh-keys ...