Possibly here? https://www.brosa.com.au/collections/gas-lift-bed-frames?gclid=CMfW-Pzu3csCFYcrvQod5loHBQ but possibly only lifts to angle rather than up and flat... Would solve my dilemma of no linen closet!

Try hospital suppliers?

Our bed has both ensemble and mattress on top of the wooden slats that you'd normally just chuck the mattress on. It makes the bed noticeably higher; pretty much on par with your example photo actually.

It's easy to change the linen, plus easier to get out of for taller folks. (We're 6' and 6'2" respectively, so use that as a guideline.)

No special costs required, so long as the slats are able to hold the extra weight the ensemble adds; which isn't much, generally - all the weight is in the mattress.

At worst, you may need to run an extra support piece down the middle under the slats if you're looking at a queen/king size and it doesn't already have a middle support. Which it should.

EDIT: You'll need something like these to go around the ensemble to stop it looking crappy. I suppose you could use a fitted sheet, in a pinch, but these are easy to put on and look very neat. Bed Wrap