I'm also seeing this problem on a recently updated Ubuntu 20.10 (soon to be release). On request of the ubuntu bug replier, I tried to compile 1.0.31 myself and both master and 1.0.31 don't have this problem. I can even use the packaged scanimage if I replace the packaged libsane-plustek.so.1 with my compiled version.
So, there seems to be a packaging/compilation problem with the libsane-plustek.so.1 lib in the current package, both in Debian dev and Ubuntu 20.10 beta. Martin -- If 'but' was any useful, it would be a logic operator
