As mentioned earlier, this is a basic update for 1.21.3. The protocol we utilize doesn't seem to have changed, thankfully.

Let me know if you find any bugs or similar, but through my testing I didn't find any issues.

Note that this also should retain support for 1.21.1 and possibly 1.21.2, but, as is stated in the main post troubleshooting section, it's not guaranteed.