I thought I should add some Info about the changes in 2.0.27-RC1:
- Comms: Added support for MAVLink 2
- GraphView: Added support for unit data in flashlogs
- Tuning Setup: Adapted extended tuning to arducopter 3.6 Fixes #1138
- Tuning Setup: Basic tuning adapted parameter names for arducopter 3.6
- MavLink Inspector: Added simple MAVLink statistics
- GraphView: Mode will now be read correctly from tlogs. Fixes #1155
- Radio Setup: Added compatibility for MAVLink 2 and increased to 16 channels. Fixes #1153
Discussion about Pixhawk 4 support for firmware update is moved to https://discuss.ardupilot.org/t/pixhawk4-install-hangs-apm-planner/35249