Uh, that's gonna be hard to do with Reddit ending it's API
Lemmy
Everything about Lemmy; bugs, gripes, praises, and advocacy.
For discussion about the lemmy.ml instance, go to !meta@lemmy.ml.
I wonder how hard it will be to just scrape the HTML to accomplish this. It'd be a bit of a cat-and-mouse game, but you'd probably get pretty far just using Google's user agent string. I kind of think Reddit wouldn't actually care about scraping vs API access, since all of Reddit's dumbfuckery seems to be coming from spez panicking due to investor pressure, and I'd bet investors don't have the faintest idea what "scraping" is.
They're using RSS feeds. Not the API. Shouldn't be affected.
Also, the API isn't closing. Devs will just need to pay for it if they go over some limits (which were increased since the blackout protest).
Shameless plug: have you seen !requests@lemmit.online @lemmit.online?
Source code here: https://gitlab.com/sab_from_earth/lemmit
It's not entirely what you asked for, but I haven't seen anything that's like it either.
Are posts made to those communities added back into Reddit?
No, it's a one way sync.