Thanks for the heads up about not being able to dismantle new ladders. Mine is pretty old (and v heavy).
My ladder standoff is rubbish. After you hook it on you have to tighten 4 wing nuts. I keep meaning to buy the ones that have a spring clamp,eg https://www.screwfix.com/p/ladder-stand-off/3571p
You can get standoffs which have a v profile
in the middle for working on the corner of a building.
Stabalising ladders. I did purchase the Ankalad ladder stay.
It allows you to use a standard ladder like the Werner combi ladder. Look at the photos in my link. It works well but the telescopic legs cant be opened out properly if the ladder is used on a terraced house next to the neighbour's garden wall. When I first used it I found climbing up from the ground section to the second section slightly odd- when you start ascending the ground section there is absolutely no ladder flexing, when you get on to the second section you then notice the ladder flex (only because of the lack of flex in the lower section).
To fit it you need to drill 4 holes for the top and bottom bolts and IIRC two tiny holes for the straps used to secure it to the ladder when not in use. I additionally purchased the Ankalad adjustable feet which allowed either the left or right ladder feet to accommodate up to about 4 inches in differential heights for unlevel ground.
I haven't used any of the other anti-slip devices on the market, although I have used bags of sand to "foot" the ladder in the past...
I only ever used the Ankalad with my two stage ladder (which my brother borrowed and never returned when he moved to the middle of nowhere). I will buy another at some point but these days I normally work off scaffolding when painting exteriors (it is more cost effective, safer and more convenient).
Something else you may want to additionally consider is ladder mitts if you have painted rendered walls.
They slide over the top of the ladder and prevent the risk of leaving black marks.