Chances are, as there was a lot of destruction and drekir from the getgo will need to assemble tools from what they can, that early survivors would likely learn very basic flake making flintknapping techniques as a part of a wide array of tool manufacture methods to get by and, over time, those early findings would be polished into somewhat more complex systems of manufacture that fit their paradigm, needs, and the history and perspectives of both those early survivors and their descendants

so first to answer real quick, where do metals fall?
Technology is not really uniform in the dragonscape, different regions invested in different methods of tool manufacture and jewelry manufacture for tons of regions but... speaking reductively, many regions engage in both metal processing and lithic production.
Generally lithics offer advantages of speed of manufacture and portability once you know how to do it, while metal tools like copper or bronze are more lasting, lithics are simply more convinient and quite possibly more abundant, especially accounting that some regions don't have many ruins or native copper resources to begin with
but in many societies you see a more "Chalcolithic" state where a mix of metal and stone/glass/etc. are used for different things. There is a reason the Chalcolithic (Copper stone) existed and lithic utilitarian tools were being used all the way through the BCs of the world in conjunction with copper, bronze, and even Iron tools generally due to local cultural preferences and reasons, same applies with drekir but speaking very broadly
many cultures have varying levels of investment in both, usually for different tasks (my obsidian blades for meat, my copper adze is for trees etc.)

So Drek flintknapping systems might lean more Lavellois-esque: Prepared Core Systems
Chances are 1st gen survivors having to make blades in the moment, would likely just learn a very basic "make a flake, cut the meat with that" sorta perspective which existed throughout the Paleolithic of hominids too (fast, frugal easy, not much skill needed, disposable blade)
So chances are their techniques would grow in complexity from that perspective. So instead of say, creating a biface, they would likely learn how to make cores from natural or scavenged sources that would ideally flake as is into a flake that is more or less the desired shape, already sharp and ready to go
There are a lot of terms for this but was a very famous technique of Neanderthals and early Modern Humans and gave rise to a whole industry with the system known as the "Lavellois system of flintknapping". you can also find similar processes used all the way to recently with groups like the Aztecs manufacturing prepared obsidian cores to produce long straight blades in conjunction with other systems of flintknapping. We can also understand these as the "prepared core methods"
Making a prepared core is... relatively hard, not the easiest thing but once it is made its very easy and quick to crank out dozens of similarly shaped blades. Some setups produce very large hand sized oval flakes, or mediumish triangular flakes, or small straight ones, there is a lot of variation archaeologically and drekir would probably find a groove in their regions and stick with that, if you can make a large triangle that is more or less good to go as a spearpoint, then that's great, just make a "spear shaped flake" as many a paleolithic dude named [insert long lost language name here] did. Same goes with things like projectile points, knife blades, etc.
of course also you can continue to pressureflake these flakes to make more complex shapes (though often this isn't necessary but it did happen)
The other big advantage is portability and resource efficiency. Generally prepared cores result in a bit less of a mess than if you were removing flakes with the goal of working a core into a biface so, on top of not getting a bunch of razor sharp shards everywhere, you save more of it for making razor sharp shards that you want. You can stow a glass pane turned atlatl dart head core somewhere until you need to get more out, then just bust that sucker and break a couple new ones off and you're good to go. Same goes with Portability. A Pastoralist is probably gonna like that they can just bust out that core they made a while ago and break off a new blade as needed rather than working metal. Its no prob

So what are drekir knappiing anyways?
A mix of scavenged, magic and natural lithics more or less.
Natural lithics can be found in abundance in many parts of the Americas, from Texas Chert to Colombian Obsidian, there are going to be natural resources that local lizards are not paying for wanting. There are dozens of these from the well known Flint and Obsidian to Dacite and some varieties of Basalt and Quartz to Agate... not listing them here.
Scavithics Are artificially made things that can be knapped to some degree, thanks to a high silica content.
Many varities of glass are readily knapped of they're relatively thick. Everything from old tv screens and beer bottle bottoms to carbon fiber glass and many a variety of window glass (not windshield different thing) Additionally Porcelains or other high quality ceramics can also be knapped, Toilet shards and many of the creme of the crop clay tiles can be worked though they are notably hard to do right. But in skilled hands can produce results.

Manaflint and Spellglass (Expect the names to swap around, sometimes I say Spellflint and Managlass, sorry its easy to forget the consistency thing)
Magical materials are also very popular and are probably the most interesting. Both Manaflint and Spellglass are made in the same manner, a relatively quick and very strong compression of mana can indeed compress it into a solid form. Manaflint and Spellglass are made by the same process of compression, just spellglass is when more compression™️ These do act like cryptocrystallines and form conchoidal fractures (IE, act like Flint). Though they have to be actively made by the drekir. Overall while mana varies, its generally pretty easy to get your hands on and making manaflint that can be processed is pretty easy if you have a very big rock and a pit to pour mana into.
As these are mana objects they can be elementized or alchemically treated which is a big deal, while the latter will take a few centuries to really start appearing the former (elementization) is alive and well in the Awakening period. Through the compression of fire mana you wind up with fireflint/glass, acid mana = acidflint/glass etc.
And as mana is just exuding a "type of energy" so too does the flint or glass. If its made of fire mana expect it to burn with red hot energy, if its made of ice mana the oppossite, electric flint might also be the worst way to get tazed in draconic history, etc.
And of course, like all unstabilized mana materials, these materials will sublimate away, with manaflint and spellglass being particularly short lived and often only making it up to about 2 weeks before it starts to crumble from sublimation. The only real difference between manaflint and spellglass is intensity of magic. Manaflint has a less intense release of magical energy but lasts longer. Spellglass has a more intense release of magical energy but lasts shorter.

Fireflint is going to be hot and will definitely get your water hot, fireglass will probably immediately boil your water.
Electricflint is going to feel like a weak tazer, electricglass will probably stop your heart and/or zap you from afar

etc.
So manaflint is generally more popular but both are used, both in unelementized and elementized forms.

You often see them used in pretty crazy ways, a fireflint sickle (seen above) might be used to slowly burn through a tree, fireflint is also used as a heatsource to help cold bloods weather winter weather. Electric flint is popular for hunting and warfare, its not great to get stabbed and tazed at the same time. Acid flint is more used than actual acid mages and is often seen in scavenging operations to cut through concrete rubble
etc. unelementized flint is also used as a sort of cheap, short term blade that is even more disposable than a natural flake

In any case
While drekir work plenty of metal, lithics fill an important niche for many a lizard picking through the ruins of old