What would it take to upgrade my 27” 212/2013 iMac to the lastest operating system (so Ventura or Sonoma)

2012 and 2013 iMacs cannot be upgraded beyond Catalina. See information in Identify your iMac model - Apple Support

It doesn't matter what hardware upgrades you would do, it still cannot be upgraded beyond Catalina.

fishprincess wrote:

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You can't upgrade your Mac's operating system beyond Catalina.

I don't know what photo editing software you have, or if you ever plan to do more editing than what Apple's Photos program supports. (It's very good for cropping and basic touch-ups; for preparing files of the proper aspect ratios for common print sizes. Not so much for heavy-duty editing.)

But IF you ever find yourself looking for more advanced photo software, I believe you'll find that Adobe (the 800 lb gorilla of photo software) no longer offers products for Catalina. I'm just trying to make you aware of alternatives – in case you're in a boat like "I wish I had bought Photoshop Elements while that program was still compatible with my Mac."

As mentioned it cannot be done, but to continue using it...

Mostly you just need a more modern Browser than Safari on Catalina, Mojave, or High Sierra like Firefox or Brave.

https://brave.com/

https://www.mozilla.org/en-US/firefox/83.0/system-requirements/

Firefox 83.0 System Requirements (mozilla.org)

Opera…Thanks

https://www.opera.com/download/requirements

Opera system requirements | Opera

Thanks to dialabrain…

Firefox 115 is now the current version. runs in High Sierra.

119.0.1 is now the current version and requires 10.15 or later.

https://www.mozilla.org/en-US/firefox/new/

Thanks to A Brody, Browsers by Mac operating system…

Browsers by Mac operating system - Apple Community

Also, Look into the Free LibreOffice, it handles MS Office files like Word & Excel, & Page Layout…

https://www.libreoffice.org/

I don't believe that Adobe still offers versions of any of their photo editing programs that will run on Catalina.

If you need a photo editor that runs on Catalina, and can handle layers (or other stuff that Photos can't), that would seem to leave

• Affinity Photo V2
• GNU Image Manipulation Program
• GraphicConverter

Affinity Photo V2 and GraphicConverter are commercial programs. They are available directly from their developers or through the App Store. The App Store version of GraphicConverter lacks several features of the version that you can get directly from the developer.

GIMP is free. The GIMP team warns that "GIMP team does not provide any package on Apple's App Store at the moment. Any downloads on the store are created by third party and is not in anyway connected to the GIMP team."

You might want to check and see what the version of iMovie installed on your Mac can do.

I don't think you can get any of the Adobe video editing programs for Catalina. Apple's Final Cut Pro isn't available for Catalina. Nor is the free version of DaVinci Resolve (if I'm not mistaken).

I'm not too familiar with the video editing programs out there, so this is something where you may have to do some digging to identify programs – and then to figure out which, if any, might still be compatible with Catalina.

https://www.reddit.com/r/mac/comments/4aqnio/good_free_video_editing_software_for_mac/