At this point, you should have received a few on-screen notices. Given your question, I think you didn’t read them.
So again, for anybody who missed on this piece of information, the new editor has a “source mode” that works in the same way as the legacy editor.
Didn’t spot that. Just checked and it looks 98% almost like the old one. Looks like I’ll have to get back to doing some CSS to get it to look like the old one.