When I was browsing Lutron's website today, I saw a notice when I was looking in their fluorescent ballast section that said:

Notice: Lutron will stop selling ballasts by the end of 2023
Ballasts are available now only for a limited time and in short supply. If you currently have fluorescent lamps, upgrading is as easy as replacing those lamps and ballasts with LED lamps and drivers. Don't get left in the dark. Learn more about simple and available retrofit solutions.

I guess this means the end of dimmable fluorescent ballasts, because I don't know of any other manufacturers still making them.

Wait, they still make dimmable fluorescent ballasts?

For the rest of the year, yes.

Yeah, I was more surprised they make them. I wonder what retrofit solution do they recommend, I'm not aware of any ballast drop in LEDs that are dimmable but I do know of some direct wire LED retrofits that dim with standard LED dimmer switches.

As for normal ballasts, I suppose they might remain on sale for longer and as replacements for systems with ballast compatible LEDs. IIRC LEDvance makes a LED T8 "ballast" that's basically a instant start T8 ballast but labelled as LED only.