treeschanger there are lots of lovely native blue flowered plants. However I've yet to see one that has a similiar form/shape to agapanthus.
Damperia is a ground cover, ( I've tried growing it several times and never have any luck but keep trying, lechenaulti ( wimpy looking floppy flowers), wahlenbergia - could end up as a tangled, straggly mess of very pretty blue from the images online I've seen., wisteria- arghh pass as I don't like climbing plants even though wisteria is pretty as well. Scabiosa ‘Butterfly Blue' (Pincushion flower) - looks pretty but is quite small. you forgot native wood violets and viola. I have both.
They all look like they'd be suited to a native cottage garden type look.
None look to be a suitable size and shape replacement for agapanthus.
I've got a nice native, weeping shrub (grows to 3m) which has blue flowers just waiting to go in here. With the cooler weather I might have to hassle a teen child into digging a hole or 2 for me since I'm still banned from gardening.( digging/weeding/lifting)