How to get --all-features to work again?

Tried the suggestions in #3897 as well but no matter what I try I cannot get rust-analyzer to activate all features.

nvim_lsp.rust_analyzer.setup {
    on_attach = custom_attach,
    root_dir = nvim_lsp.util.root_pattern("Cargo.toml", "rust-project.json"),
    settings = {
      ["rust-analyzer"] = {
          ["cargo"] = {
              ["allFeatures"] = true,
          },
          ["checkOnSave"] = {
              ["allFeatures"] = true,
              ["extraArgs"] = {"--all-features"},
          }
      }
    }
}

Currently at commit aa38fa1

Start by reproducing the configuration using Cargo.toml or rust-project.json as the root and the shown rust-analyzer cargo.allFeatures and checkOnSave settings. Compare behavior at commit aa38fa1 and verify completion or diagnostics with all Cargo features enabled; done means the configuration reliably activates all features.