I just want a quick cooker / steamer with simple, but somewhat extended basic controls. If it could offer a clear-top lid and simmer options, it could be used to make soup, which would be incredible.
[...]
I'm especially interested to know about ideal material designs and surface lining ethics because I won't do "non-stick" plastics that overheat and crisp off into my meals.
As someone who cooks rice (or alt grains like quinoa) almost daily, trust me when I say this - just get any decent fully stainless steel saucepan, which has a glass lid and a steamer basket option, and you're all set. For example, something like this: https://www.amazon.com.au/HZIB-Stainless-Hanging-Saucepan-Nonstick/dp/B099Z6KQJJ
It would be free of PFAs (aka "forever chemicals" like Teflon, GenX etc); zero plastic means it's eco-friendly and there's little risk of getting microplastics into your food; and it also makes it dishwasher/steel wool safe. Cleaning it manually is also a lot easier compared to a full-on rice cooker/instant pot.
Cooking rice in one of these is super easy - just add 1.5-2x water, bring it to boil, add some rice, turn down the heat and let it simmer for 12-15 minutes. Take it off the stove and let it cool down for 5 more minutes and you're done. Perfectly cooked rice every time, no sticky bits either, which makes it super easy to clean up manually as well.
If you want some of the more fancier features found in electric rice cookers then just get an induction hob (you can get portable ones, which are pretty cheap like < $100). With a modern induction hob, you can set an automatic timer, schedule it, and even select from preset programs like soup/steam etc, so you can make it behave pretty much like a rice cooker.
The other advantage of using an induction top (over regular electric or gas) is that your saucepan's base won't get dirty, which will save you the hassle of cleaning it, and thus it'll continue to retain it's heat transfer efficiency without you needing to put in any cleaning effort.
IMO, this sort of setup gives you so many more advantages over a fancy cooker and is a much better option. In addition to the low cost, low-fuss maintenance, and eco-friendlyness, you get versatility - like you could even chuck the whole thing into an oven if you wanted to, say in case you feel like making cake or something.