I have Lightroom 3, recently updated to mac os catalina, now I cant open Lightroom.

See the screen capture from Adobe's post with respect to support with macOS 10.15 Catalina. This post was issued by Adobe several weeks prior to the release of Catalina for macOS.

One glaring by the way. By Lightroom 3, you are refering to the old standalone vetsion?

Not the new cloud centric vetsion?

Correct?

I may have made a bad assumption that I based on due to the error message.

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I posted here because adobe tech support told me this is the place to post and I'll get help from actual employees. I told her that didn't make any sense but she was quite insistent 

Probably because you unfortunately talked to one of the less capable outsourced Adobe techs, that probably is following an SOP to not provide support for a sunsetted product as Adobe no longer officially supports v6 and older.

And, that could work, Lots and lots of fellow members to in fact provide that assistance in this community site.

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Now getting v6 to work would not be at all hard, as long as it is installed before upgrading the MACOS to Catalina. After upgrading to Catalina is a no go.

This all relates to MACOS refusing to run 32 bit apps. And the installer for v6 and older is 32bit, so while 64bit v6 will work, it cannot get installed.

As for v3, hmm, is that 64bit? if 32 bit, then not only can you not install, but you cannot run. (update, 64bit ssupport sstarted at v2, but at that time , or more specifically upon v3, was 32 vs 64ban option, and if so what was installed?)

The error message makes me think 32bit.

Other members will probably correct me if wrong.

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see:

https://helpx.adobe.com/lightroom-classic/kb/macos-catalina-compatibility.html

https://www.lightroomqueen.com/lightroom-macos-catalina-compatibility/

If you want an actual official Adobe response, then post your problem over at the official Adobe feedback site where Actual Adobe employees, Adobe Techs,  actually respond. As opposed to this Community site,  that is for Adobe customers to interact.  No, or very few actual Adobe employees to be rude to at this site.

That site being:

 https://feedback.photoshop.com/photoshop_family/categories/photoshop_family_photoshop_lightroom?topic-list[settings][type]=problem

Lightroom 3 is so old that it will not run on Catalina.