Where is the QGC-32bit for ubuntu?

where is the QGC-32bit for ubuntu??? I only find the QGC-64bit for ubuntu !!!

There is no 32 bit build. Given that 32bit x86 processors are not getting manufactured anymore for ~10 years it makes limited sense for us to offer. If your system is fast enough to run Qt5 then you should be using 64bit. Note that you can run 32bit applications on a 64Bit Linux.