Where normally, these two services differ drastically. Usually, Infinity (or any other Reddit client), would talk to the Reddit API. Converting them to talk to the Lemmy API is like converting them to speak a whole other language. There are ideas and proof-of-concept projects to translate between the two.

The software would sit in between a Reddit client and a Lemmy instance. Receiving Reddit "language" from the client, translating to Lemmy "language" on the other side, and doing the reverse with the response it receives from the Lemmy instance.

If such a piece of software existed, a Reddit client could be converted simply by saying: "Instead of talking to the Reddit API, talk to this server". The client would still "speak" the Reddit "language" with the translator, but interact with Lemmy at the other end.

It would take the time pressure off of Reddit third-party client developers, giving them time to properly convert their applications to their new preferred platform. It is a large task though, so I'm not sure if it'll be usable by the time Reddit disables free API access.

Would be very nice to have, as the bar set for UI and UX design by most third-party Reddit applications is very high (specifically shout out to Apollo and Infinity). Apps like Jerboa or Mlem couldn't possibly reach that level of quality within a month.