npub1j8rtgsahj0fy4kq4s955c57wmpk2f09yd0v5jrlnujg6gmmqvz8szv23jk (npub1j8r…23jk) npub1j46f9va5qdrmamcwmncew7g8mwekgma386dhws6k04fsnlkqpcpsj23gm7 (npub1j46…3gm7)
Depends on the instance, but Mastodon does support sending longer posts.
All ActivityPub things kindof have to at least support reading them.