Would a cheap Lexus CT 200H with lots of miles be worth it?

Goudy

The 12v battery will usually start to charge when the car is turned on to "Ready".
It will take power from the traction battery, but that can take some time.

The traction battery won't run all the way down, it really only works down to 40%.
(but you can force the engine to run and charge the traction battery if there is ever a need. Just turn it on to ready, hold your left foot hard on the brake pedal and clog the throttle pedal, the engine will run up and within a couple of minutes it will fully charge the traction battery, full is 80% remember).

What owners are finding and some dealers are recommending it using a solar trickle charger like these.
Best solar chargers for car batteries 2024 | Auto Express
It won't charge a flat battery, but they keep the battery chemistry active enough to prevent them going flat, if it's placed in the light of course.

Most will plug and unplug direct into the car's OBD2 port, so no messing under the bonnet/boot.

I have one of these in the mother in laws car at the moment. It's actually mine but needs must (that is to keep the in law happy and stop me being called out)
AA 12 V Car Solar Battery Trickle Charger, AA1432 - for Vehicles and Caravans - Battery Connectors Included, Solar 4.8W, Black : Amazon.co.uk: Electronics & Photo

It's not a hybrid, but it does get left stood for long periods, sometimes for 2 months or so (she really needs to give up driving and sell it)
The cars 12v battery seems to hold charge well and has never been a problem.
She also seems to handle plugging it in and out no problem once shown.

chssvl

Amazing, thanks! Living in a flat, I don't really have a way to use a mains charger so this is super useful. This was also the reason why I considered, but ultimately rejected the option of getting a BMW i3 (likely REX). Pricing seemed right and it definitely seemed rather cool, but feels like the public charging infrastructure is not quite right at the moment to completely rely on it.