PyQt5 fails to build on Yocto/boot2qt with 5.15.0 manifest

Licensed user building boot2qt for Toradex Colibri-imx7.  Trying to activate python3-pyqt5 on the default build layers by adding
 
CORE_IMAGE_EXTRA_INSTALL += "python3-pyqt5"

The build proceeds until it tries to build PyQt5, which results in this error:

Querying qmake about your Qt installation...
Reading configuration from /lkoziarz/qt-fifteen/build-colibri-imx7/tmp/work/cortexa7t2hf-neon-poky-linux-gnueabi/python3-pyqt5/5.13.2-r0/PyQt5-5.13.2/pyqt.cfg...
This is the GPL version of PyQt 5.13.2 (licensed under the GNU General Public License) for Python 3.7.6 on linux.
Type 'L' to view the license.
Type 'yes' to accept the terms of the license.
Type 'no' to decline the terms of the license.
Do you accept the terms of the license? Error: This version of PyQt5 requires sip 4.19.19 or later.

The current recipe for sip in /meta-openembedded/meta-oe/recipes-devtools/sip is 4.19.16.  Changing this recipe to 4.19.19 results in a successful build and PySide2 runs on target hardware.

The notes from Riverbank also imply that this will break again when 5.15.1 is released:

https://www.riverbankcomputing.com/static/Downloads/PyQt5/ChangeLog-5.15.1.dev2006010132

• lib/pyproject.toml:
  SIP v5.3 is now a minimum requirement.
  [c88d94dfb85b] <5.14-maint>