here's what Viva Tubes has to say about supply:
Tube Shortage Update - Scarce & In-Stock
As time goes on, some areas are improving while others are worsening. We expect things to stay the same for the foreseeable future. As it stands now, there is typically enough supply to keep the world's amplifiers humming. Choices amongst brands and sub-types will remain touch-and-go but there is no reason to panic.
Scarce as of March 2023: KT88, KT66, KT77, 6550, 6L6GC, KT120, KT50, KT170, 300B, 2A3, 6L6G, 12AY7, 12DW7 & certain brands of 12AX7.
You may notice that many of these are unavailable on platforms such as Amazon and also from tube vendors as well.
We are well-stocked on all of these types aside from KT120 & KT150.