The novel is officially translated on Webnovel, and you can read it all for free if you're patient.
If you're not patient, an internet search for "read the king's avatar chapter <x>" should suffice.
Well, webnovel is good, but I kindda hate the lock feature :| You can read here if you like: https://readlightnovels.net/the-kings-avatar.html
Ps: that's for novel, I don't read much manga, but usually I read at mangakakalot: https://mangakakalot.com/read-qm7oa158504832308
You can read at https://novelfever.com/book/the-king39s-avatar
What do you think?