“Tubeless” tires don’t stop flats from happening. The sealant used in the tires stop flats. Sealant in tubes will do the same. You should also remove the object causing the puncture no matter what system you are using. A thorn in the tire is going to flex and open the puncture each time it flexes. It won’t seal properly and will continue to leak.

Sealant isn’t perfect either. I’ve been on rides where people using sealant had flats (because they didn’t remove the thorn) and I, using plastic tire liners and regular tubes, didn’t. Some of it was luck, some of it was knowing where the goatheads were going to be the worst and not plowing though them. Don’t mock the Goathead Gods, however. I got smacked the next time I did the ride because I mocked them.

Personally, I don’t use sealant for a couple of reasons. It can be very mess both in installation and during use. Every time someone comes into the local co-op to install tubeless, everyone disappears because they don’t want to deal with the mess. A blowout becomes a very different event with sealant. The sealant also dries out, whether in a tube or tire and the rate of “drying” is related to temperature.

I’ve used...and had good luck...with tire liners for the last 40 years. No, it’s not perfect but neither is sealant.