Long promised from companies but never delivered. Now you can print your own. No more flats

https://www.yankodesign.com/2026/08/07/you-still-cant-buy-airless-tires-even-after-a-decade-but-you-can-3d-print-one/

I built & rebuilt assorted hybrid bike styles when 8-12 yo. One had solid tires. You absolutely could not ride it on icy or slushy roads as the tires would slip out from under you sideways.  It was great for long, skidding braking and drifting, though.

I bought some high-$$ airless-but-spongey tires for the tandem 15 yrs ago. They still sucked. The design of the one posted above looks promising.