You're very welcome!
FWIW, I recently "retired" both my 2010 & 2011 MacBook Pro laptops, primarily due to logic board issues ... but, also because neither could run anything newer than macOS High Sierra.
Your 2012 iMac, fortunately, can run up to Catalina, but even that version is no longer getting updates from Apple. Apple basically only provides updates for the three most recent macOS versions. Currently, those would be: Monterey, Ventura, & Sonoma.
This is where you have to decide on how much you want to continue to invest in a obsolete Mac. If getting a newer model, even a refurbished one, it not an option, I would offer the following on what I would do with this Mac. Note that some of these would require opening your iMac ... not necessarily an easy task. You can go to the iFixit site to get an idea on what that would entail.
- Remove or replace the existing SSD with one with a larger capacity. SSD prices have come down significantly in the recent years.
- Remove or replace the existing HDD. Your current one is a 7200-rpm drive, and this is what you will want. What size will really depend on your needs.
- Leave the current RAM configuration alone. 32 GB is plenty for just about anything you can want to use this Mac for.
- Downgrade to macOS Mojave. I only recommend this because of the issues you are seeing with Catalina, otherwise, I typically never recommend downgrading. You can try external bootable SSD with various versions of macOS to see which works best for you. Ref: Use an external SSD as your startup disk … - Apple Community