Erlang guarantees byte code compatibility across 3 versions. So we can’t provide precompiled Rebar and Hex that works from 24 all the way up to 27 (sometimes we can, but not this time). The fix would be to precompile several versions of them, we want to do for future releases.

So far I have installed ref:main using asdf and all tests have passed, so it shouldn’t be hard, right? Is it planned for v1.16.4?

Unfortunately the answer is no.

main is the future 1.17, which will be the first version to support OTP27. You can check the compatibility matrix here.

I don’t recall exactly the issue, but 1.16 can’t support both OTP24 and OTP27 at the same time, so we first have to wait for 1.17 which drops OTP24 support.