I'm pretty sure you can't. There seems to exist only 64 bit versions of Live 10: https://www.ableton.com/en/trial/

When you open Live 10 in Mojave you get this alert:

https://help.ableton.com/hc/en-us/articles/360003076340

Interesting. So it's still mixed and has disadvantages of a 64 bit program (no 32 bit plugin support 1) and of a 32 bit program (no compatibility with Catalina) while pretending to be a 64 bit program. Sounds great!

1 at least on Windows

On macOS Catalina?

The main objective is to make music. Running macOS Catalina is optional.

It's not if you're buying a new Mac from today.

Ok but we were talking about running on macOS Catalina here - you need to be 64-bit to run there. And if you don't, you're likely to get left behind.

Or, you know, having to upgrade anyway, people might switch platforms to one which has a better track record in supporting old software.