This might just be the Nextcloud download server being really slow to respond.
It’s currently taken almost a half hour to download that piece of the upgrade. I wish that piece had been downloaded first, before taking down any services.
I do not believe services are taken down, my mail reader did not show any issues checking mail during the upgrade.
Indeed it took a while for my box to download 2x 80MB (first the 16.x and than the 17.x) Maybe with slow download a progress idicator would be nice. To see why it took so long I checked forst how big the file by downloading the same file from my windows machine (file location can be seen through top -c ) than I checked once in a few minutes the size of nextcloud.zip through /tmp via ls -la Than it was just wait wait (yes I had 2 consoles open)