Hello AUR Users,
The RPC version 1-4 deprecation period has now ended. At this time, users should rely on the fact that support for version 1-4 may be dropped at any time.
If you own a project which uses the RPC API, you'll want to comply with the version 5 API immediately. See the Deprecation Notice  for a more elaborate explanation of the deprecation and how to move forward.
Deprecation warning which was patched into the RPC API 31 days ago:
The use of versions lower than 5 is now deprecated and will soon be unsupported. To ensure your API client supports the change without issue, it should use version 5 and adjust for any changes in the API interface. See https://aur.archlinux.org/rpc for documentation related to v5.
Again, if you have not yet migrated, now is the time to do so. Completion of the FastAPI port is quite near to completion, and when we deploy FastAPI in production on aur.archlinux.org, support for 1-4 will be non-existent.
Thank you all for your selfless contributions to user-driven software as a whole. You are what makes the AUR a usable and attractive feature of Arch Linux and keeps developers wanting to improve the project in general.
References:  https://lists.archlinux.org/pipermail/aur-general/2021-September/036579.html
Thank you for your attention, Kevin 'kevr' Morris