Update 25 June 2023.
Current status: ‘My’ tadpoles are turning into frogs. Most have hindlegs, many now also have forelegs, but there is still a sizeable number of individuals that have neither yet.
The original egg clutch observation contains links to all other subsequent related observations:
https://www.inaturalist.org/observations/152129220
Feeding: In addition to leaves (Taraxacum, Lamium, Plantago) and the odd strawberry, they very much love spirulina wafers. I had assumed that my supply of fish food (photo below) would last until the moment they would become terrestrial, but not so.
Behaviour: Those further along in development now spend most time floating on the surface of the water with the tip of the snout out of the water, or continue to rest on floating leaves (tadpoles in all stages of development do this frequently). Assuming that the older ones would appreciate a somewhat sturdier surface, I purchased a floating turtle platform. Turns out they do:
The current setup: Container with the platform and netting, protected by a sort of fence of cage elements.
The net is there to keep the snakes out. On different occasions I caught two juveniles by pure chance while they were diving in the container and on another I saw a third one slither away in the vegetation:
https://www.inaturalist.org/observations/168716203
https://www.inaturalist.org/observations/165191129
The cage elements were there originally to keep my dogs from jumping into the water.