According to some articles from BAIDU.com, lots of users do updated deepin v20 from v15, quite different architectures to some degree, but not using a single bash-command line other than that as below:
first of all, have to change the source:
sudo vi /etc/apt/source.list
deb [by-hash=force] https://community-packages.deepin.com/deepin/ apricot main contrib non-free
using # to comment out previous source
and then,
sudo apt-get update
sudo apt-get dist-upgrade -y
finally, other in terminal or desktop evironment, you can see that you have updated to v20.
BUT, THE KERNEL IS STILL NOT UPGRADED!!!!!
so, i think you can take a try where release, and see what if...
When the Deepin 23 is released it will be possible update from Deepin 20.9 to Deepin 23?