what will work or work best , depends alot on the lock .
A couple of my personal rifles simply don’t do well with English flints . But the love French amber. Others don’t like French amber but do very well with English .
Then you have the cut agates. They work and will spark but as was said , they need to be sharpened on a stone or with a diamond file . They also a lot of times will eat up a perfectly good frizzen but will at other times work on a frizzen that’s on the rather hard side .
I have on occasion used agate spalls they work and can be napped .
Chert works as well .
As to whats new , well there is always someone trying to improve on something that ,,, well frankly doesn’t need or most likely cant be improved on .
one such so called improvement I saw recently what where someone had taken a striker from a cigarette lighter and fitted it to a block . I guess they then too glue strips of lighter flints on the frizzen ????I about died laughing when I saw it , but I guess it does work . I save a photo somewhere
