I agree with the other comments, wait until you white wash, but I would be tempted to paint some colour of the walls if you cannot remove the trim (it might be there to tidy up the joins).

I can’t quite see the photo clearly enough to comment but in real life I’ve seen floor coloured gap filler used, and also mini quad. The mini quad will involve some tricky angle cuts but give you the best finish without pulling up the floors. PS I have the same plaster, it’s impossible to patch particularly if it’s textured. One hint, if you’re doing more work on your house. In one clumsy kids bedroom I’m using a VJ lining panel up to the picture rail. Saves matching or patching the old plaster.

some of the older carpenters and cabinetmakers will have the necessary traditional planes for cutting these profiles or you could have one made out of plaster, cement.or builders bog moulded out of a cast made from the remnants of the original board or try a high tech solution with a copy made with a 3D printer or two separate lengths of moulded timber attached together to approximately match the original but you'll need to research plaster works, restoration companies, specialist carpenters and tech colleges for a computer, woodworking or art student keen to try an interesting project but you may find that it's quicker and easier to replace the whole section with an unmatched section of plain skirting board or try stealing a section from somewhere else in the house where the skirting board is hidden behind a bed or lounge and replace the hidden area with the plain board...best of luck with your repairs

Hi AW my photos are only two. The other four photos are from houzz. I search bedroom in Perth. As we still build with concrete slab and double brick walls over here in the west. Gradually changing to other build types. In WA, You have to specifically ask the builders over here to install skirting boards if you what them. They are not included in the normal build. I think the look is fine.