"Up to date" and "flexi" contradict each other. Around the time that mesh bodies like Athena hit OpenSim, rigged mesh hair was the hot shit, and it still is, and flexi hair was dead.
There is no flexi hair that's as up-to-date as Legacy and EvoX.
And especially, there is no rigged flexi hair. If you get flexi hair, you WILL have to adjust it yourself. Mesh cannot be flexi.
If you want up-to-date hair, get ripped Doux hair. But it's un-flexi rigged mesh.
If you want flexi hair, look here, but all flexi hair is probably well over 10 years old now:
https://opensimworld.com/hop/84040