Google Hangouts on Mac Catalina

Solution 1:

As far as i remember (afair), there was native Ggl Hangouts app (with 32bit components) for older macOS, but Ggl discontinued to share those files. Even if it was obtained it will not run in Catalina.

So an option that regular or power users can do is, use Wine-project software, it is an emulator type of software, it allows to run Windows app in macOS/Linux/Unix, etc,

• and afaik the project & project's users have began to collaborate+work on supporting 64bit-only macOS (Catalina, Big Sur, etc).
  It is better for this case that Wine is installed by using a package-management type of software, (if Ggl Hangouts was available as stable option, and you were using 32bit supported macOS, then installing Wine directly w/o pkg-mngmt sw would've been fine).
  See this answer here (Load Wine by using MacPorts).
  ( MacPorts is a package-management type of software )
  ( Homebrew (is also another package-management software, but it) violates Privacy-Rights and creates risks^{1, 2, 3, 4, 5, 6, ...}, so i will not suggest to use that, but you are free to choose whatever you want to use )

GH = Google-Hangouts.

There was also a native Ggl Hangouts 32bit app for Windows, but Ggl discontinued files for this too, but some caching/wayback site may/can be used, to obtain it, (if you have original file's hash/checksum code known).
And another option is, if GH standalone app was already installed on a PC/Windows computer & you have access to that computer, then you need to copy Hangouts exe (executables), DLLs (lib), etc files, into your macOS computer's one of the folder, & then you can use Wine app to run the exe file in macOS/Catalina.

I have shown many/Various ways to use Google-Hangouts(GH) web-service (aka: chat network, aka: IM network) on Catalina (and Mojave) in below linked answer's EXTRA-INFO section, if you have time & respect for different choice/preferences, then read this linked answer here:
https://apple.stackexchange.com/a/400885/133434
( as i have posted the link, i will not repeat info here again )

Solution 2:

It’s probably overkill, but you can use virtualisation software such as Parallels to run an older macOS version with 32-bit support in a virtual machine, and then use Hangouts in that VM.