That looks like the fan for the convection part of the oven.
Good luck. You can clean it, but it’ll look just like that again in no time. That’s not really dirty for an oven, in my mind.
Know why commercial ovens look like they do? There’s only so much cleaning you can do in it’s down time.
I wouldn’t leave puddles of stuff in an oven, just that they’re going to get coated/caked/baked on, especially since these consumer ovens use a cheap sheet metal inside, which is very hard to clean or keep clean. It’s not stainless or an enamel, which are very hard, non-porous surfaces, which makes them easier to clean.
Most likely the owners manual says to clean it just run it on max for a period of time. That will carbonize whatever is caked on, making it easier to scrape off.
Fear of change? Hahahahaha
No, I just know what’s involved, with the unpredictable “gotcha” a year from now.
Not to mention the knowns. Holy hell switching from Windows to Linux is very problematic for typical end users. Yes, the UI is that different, even with “friendly” distros.
You say your grandma made the switch? OK, so someone who uses a browser for everything and doesn’t actually use office.
Let’s see Libre office open an excel spreadsheet with tables.
Or edit a word doc and send it back and have it not be screwed up.
Not migrating is practicing risk mitigation. Hell, I can’t change a single setting on work systems without validating that change in the lab first. And you want people to switch entire operating systems. For what?
So stop this fear projection nonsense.
(And I work with Linux every day on multiple distros).