The following packages will be upgraded:
libpython3.9 libpython3.9-dev libpython3.9-minimal libpython3.9-stdlib
python3.9 python3.9-dev python3.9-minimal
I can never remember the exact relationship between PureOS and Debian, but I think that when PureOS Crimson is released, it should contain Python 3.11. No idea on that timeline, though.
In the meantime, you can download and install a newer version of Python. The official Python website provides some downloads, though I don’t find these very convenient. I use Anaconda/Miniconda instead.