Unable to update iMac from Ventura 13 to Sonoma 14

Yo, so it's an iMac Retina 5k 2017 (not sure if this is Pro?), currently on Ventura 13.7.2.

I would like to update it to Sonoma 14, and I hope I don't sound stupid, but I feel as though my model is compatible, even if it's the iMac Pro 2017 listed [ macOS Sonoma is compatible with these computers - Apple Support ].

I go to the App Store to 'get' (download) Sonoma, as my Settings currently display no new updates (the latest was V 13.7.2 - this evening I decided to do just that), but it is unable to download the Sonoma Installer due to "Update not found", and to 'check that my model is compatible'.

My Settings are also currently telling me that my Mac is up to date (since now updating to V 13.7.2) - I have yet to restart/shut down the Mac to test if it will reset, and I will be doing that. I also have my automatic update settings set to security only, as updating to higher versions was not a precedence of mine before. I would like to presently, however - perhaps part of the issue is the restricted automatic?

You could argue that it is a memory issue, as Sonoma is 12.1 GB, however, I believe I have enough space to allow it, and am planning on spending some time to move things around anyway to make more room.

I currently have Installers for Sierra, High Sierra & Monterey on my system, and I am also unsure what to do with these (should I get rid of/bin them?), as I don't know whether they'll be useful in the future or just memory waste.

I'm not too great with the knowledge of specs., and this was the best I could find for my lack-thereof, but I hope it's enough for someone to be able to understand my circumstance? This isn't an urgent issue, but once it is done, I'm hoping it will be a relieving ending :-)

If it is the matter that my iMac is not compatible, that is absolutely fine! I've been working well and great with Ventura regardless, but just thought it would be nice for a newer update for a change. If it is compatible and I am able to update my iMac to Sonoma, that would also be sweet!

If I'm stupid, then I'm stupid lmao! It is also, like, midnight for me when writing this so haha anyways...

Thank you so much for reading my ailment!