This release includes a bump to the base Alpine Linux version as covered here: https://wiki.alpinelinux.org/wiki/Release_Notes_for_Alpine_3.13.0#time64_requirements
This will require a minimum Docker version of 19.03.9 for 32bit based systems (Arm32 or i386)
The default Node-RED Container is based on the NodeJS node:16-alpine container. This now based on Alpine 3.16 which has dropped Python2. Python2 went end of Life in April 2020 and has not received any updates since then. It really should not be being used for anything any more. As 3.0.0 is a new major release we will also be dropping Python2 entirely. Please let us know if this breaks any nodes (but also raise issues against those nodes as they need to be updated).
Other 3.0.0 release notes here: https://discourse.nodered.org/t/node-red-3-0-0-beta-4-released/64538/36