I have an older HP netbook and am looking for a 32-bit version of Ubuntu 18.04 desktop. Can you advise if one is available?
Standard Ubuntu flavour has dropped 32-bit installer for the 18.04 release aka Bionic Beaver (actually since the 17.10 release), but rest of the Ubuntu flavours still support 32-bit systems. You get them from here:
Alternatively, you can use the Ubuntu mini ISO (refer to this answer).
You can find 32 bit version is here.