ncurses6.2 in Ubuntu 20.04 - typing not visible

[Tjareson]

Hello,

I guess this is most likely not a bug in ncurses, but who knows...

In any case I don't know what else to look into anymore, so maybe
someone here can give me a hint what to investigate further to fix my issue.

I have an application which uses ncurses. I can compile it (gcc) without
any issue and it runs without problems or any further tweaks in Ubuntu
12.04, 16.04 and 18.04.

Now: it doesn't work in Ubuntu 20.04 with ncurses6.2. I'm getting it
compiled without error, but after starting the application, it works
only "half broken". (gnome terminal 3.36.2) Windows are getting drawn,
but if I type, I don't see any input. If I end the application (keys are
in general working), also the terminal is messed up, like no cursor, no
visibility of typing anymore.

I've observed such behavior if ncurses versions are getting mixed up,
but htop shows me at least consistent use of libraries:
  mem     REG     0xfd01      43576    4594631
/usr/lib/x86_64-linux-gnu/libmenuw.so.6.2
  mem     REG     0xfd01      81448    4594227
/usr/lib/x86_64-linux-gnu/libformw.so.6.2
  mem     REG     0xfd01     231504    4594675
/usr/lib/x86_64-linux-gnu/libncursesw.so.6.2

It is a fresh standard install of Ubuntu 20.04 and I've installed only
libncurses-dev additionally. (with apt install...)

I've linked the following libraries:
/usr/lib/x86_64-linux-gnu/libncursesw.so
/usr/lib/x86_64-linux-gnu/libformw.so
/usr/lib/x86_64-linux-gnu/libmenuw.so

And these are the ncurses related linker options (in codeblocks):
-lncurses++w
-lformw
-lmenuw

echo $TERM shows:
xterm-256color

Other applications like htop, mc etc. are running without any issues.

It looks like as it doesn't recognized the right terminal type or
something like this. But then, why are apps like vi working w/o any
issues in the same terminal?

Best,
Tjareson