Server: https://sysupgrade.openwrt.org
Running: 23.05.0-rc4 r23482-7fe85ce1f2 on mediatek/filogic (mercusys,mr90x-v1)
Available: 23.05.0-rc4 r23482-7fe85ce1f2
Requesting package lists...
installed package libncurses cannot be found in remote list!
Are you sure you want to continue the upgrade process? [N/y]
There's something strange going on with the sysupgrade database, see the firmware selector thread (link below).
But, you actually do have libncurses installed, it's an alias for libncurses6:
You can see what depends on it using whatdepends:
$ opkg whatdepends libncurses
Root set:
libncurses6
What depends on root set
parted 3.4-2 depends on libncurses6
libreadline8 8.1-1 depends on libncursesw6
vim-full 8.2-5 depends on libncurses6
htop 3.2.2-1 depends on libncurses6
fdisk 2.37.4-1 depends on libncursesw6