If you're still looking to get your hands on a ninth-generation Intel Core processor, you might want to act now. The company has put out a Product Change Notification (via PCWorld) that marks the discontinuation of the lineup. Customers won't be able to order the products after June 2021.
If you're wondering why you might still be considering a ninth-generation processor with 10th-generation 'Comet Lake' on the market, it's because Intel actually used the same socket for several generations. The LGA 1151 socket was used from sixth-generation 'Skylake' until ninth-gen 'Coffee Lake Refresh', although the chipset changed.
As for what specific processors are being discontinued, it's pretty much all of them from that generation, including Celeron, Pentium Gold, Core i3, Core i5, Core i7, and Core i9. That includes the standard S-series, unlocked K-series, F-series without integrated graphics, and combinations of those things.
Intel's newer Comet Lake S processors are still built on a 14nm process, unlike the 10nm mobile processors from the 'Ice Lake' family. It looks like we're going to see more 10nm products in the 11th-generation family though, but 11th-gen Rocket Lake desktop processors are set to continue using a 14nm process.