Specialized tubes have removable cores.
There's a GCN video that I can't find where they did this and then hammered a nail into the tire to see if the sealant worked in the tubes. It did.
Because of that video I tried it as kind of a poor man's tubeless alternative on a gravel bike for a while. I had very good luck with it, don't recall having any flats. Sealant isn't supposed to protect from pinch flats but it sure seemed like it did.
Eventually I got a tubeless wheelset, but I still have a couple non-tubeless bikes that I'll squirt Orange Seal in the tubes every once in a while for insurance.