Honestly, Digi-Key and Mouser continue to have decent selections in stock.
I guess it depends what you were aiming for. The individual microcontrollers (especially non-BGA ones) and almost (PICO aside) all raspberry PI boards especially, but also the Microchip ones (low cost versions, I wanted). Have mostly or fully disappeared.
Also, the various Microchip/Atmel stuff.
There are exceptions, such as the ESP32 and related things, which have generally continued to be freely available, a lot of the time.
EDIT: On reflection. Sometimes, or for long periods of time, the low cost versions of the development boards, have been available, but I tended to miss the opportunities to get them, and they went out of stock. The high priced boards, do seem to have remained in stock, throughout, in general.