The issue is the 12 speed chain. It’s more narrow and not meant to work well with the wider 11 speed cassettes. Will it work? Yes, but you’ll likely have some shifting problems.

From SRAM:
Can I use a bike built with RED or Force eTap AXS™ on my direct drive 11-speed trainer?

Direct drive trainers require XDR cassette compatibility in order to use them with a RED eTap AXS™ bike. Use of 12-speed RED chains on 11-speed cassettes is not recommended, due to incompatibility that can damage the drivetrain. SRAM has provided information to market leading direct drive trainer companies covering what’s required for compatibility with RED or Force eTap AXS™ drivetrains. Please check with your preferred trainer brand for compatibility.

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Favorite Gear: Dimond | Cadex | Desoto Sport | Hoka One One

Thanks. So I’m about to get AXS and I’m trying to decide do I wait until BF trainer sales to save legit $$ and use 11 speed non direct drive trainer until then or just bite the bullet, not risk messing up new drivetrain, and get a direct drive trainer now with XDR . Hmmmmmmm.

I have a tacx neo with 11 speed cassette. I run sram red 10 speed, ultegra di2 11 speed, and etap axs 12 speed on it. I set it up so I don't ever shift, and I have over 1000 miles on each drive train inside, and they work without problems when the bikes are used outside with proper cassettes and shifting.

Thanks. That helps. But I feel like since mine, for the interim, would be a wheel on trainer where I “have to” shift with 11 speed cassette, it might be clunkier.

Just use the wheel with the axs cassette on the wheel-on trainer. I dont really see what the problem is here? If you use the 11 speed cassette your shifting is going to be bad, and you'll probably mess up both your chain and the cassette since the distance between rollers is different with an axs chain

I have a dedicated trainer wheel/tire so my prep time In swapping wheels or tires for wknd rides is minimized but, yeah this is what I will probably do.

AXS chains use larger diameter rollers, the chain pitch is the same.
This is not compatible with any other drivetrain.