Today, a fresh copy of Debian 12 was installed with the latest pwr61_6.1.0-1_amd64.deb. It's a very nice version of Proview. So many new features, thanks!

When compiling a custom class, the same error was seen: /usr/include/rpc/rpc.h file not found. A search for rpc.h in Debian 12 did not return any results. So, the /usr/include/rpc files were copied over from Lubuntu 16.04 LTS from the same location: /usr/include/rpc/*. That fixed the issue. Thanks Claus and forum members for pointing out the issue and a fix. A Google search suggests libtirpc-devel may include the latest version of rpc.h, but have not tried it.

/Ron