I have a problem with screenshots in DOSBox ECE r4334, when using the CTRL-F5 screenshot function, it generates a zero byte file. I don't have this problem with vanilla DOSBox or other DOSBox forks, but then all the other builds are 64-bit, so that may have something to do with it.
This is on Fedora 31 64-bit and I'm using your pre-compiled 32-bit binary from "DOSBox ECE r4334 (Linux).7z"
Looking through the logs, I found this
libpng warning: Application was compiled with png.h from libpng-1.6.37
libpng warning: Application is running with png.c from libpng-1.2.57
libpng error: Incompatible libpng version in application and library
Checking what 32bit libs I have installed:
$ rpm -qa|grep libpng|grep i686
So it seems it uses the older lib while the newer one is also present.
$ rpm -ql libpng-1.6.37-2.fc31.i686
$ rpm -ql libpng12-1.2.57-10.fc31.i686
$ ls -l /usr/lib/libpng1*
lrwxrwxrwx 1 root root 18 Jul 26 2019 /usr/lib/libpng12.so.0 -> libpng12.so.0.57.0
-rwxr-xr-x 1 root root 189160 Jul 26 2019 /usr/lib/libpng12.so.0.57.0
lrwxrwxrwx 1 root root 19 Jul 26 2019 /usr/lib/libpng16.so.16 -> libpng16.so.16.37.0
-rwxr-xr-x 1 root root 255680 Jul 26 2019 /usr/lib/libpng16.so.16.37.0