screen attach a screen that is ‘attached’ after connection drop

The magic formula I used in the irssi days for all cases works here too: screen -raAd $n

screen scrollback

To change it during runtime, <C-A>:scrollback $number. Otherwise ~/screenrc:

defscrollback 1000000

nextcloud

You can drag-n-drop files from the OS to a folder in nextcloud web gui, and it will automatically upload the file directly there (and inherit all permissions)