Clangd currently has a command line option clangd --fallback-style=<string> which acts as if the same argument and its value were passed to clangd's internal clang-format. However, as with standalone clang-format, the fallback style must be one of the small handful of predefined presets provided.
Standalone clang-format has an additional argument clang-format --style=<string> which allows for fine-grained control over individual style parameters from the command line. This functionality would also be useful in clangd for hopefully obvious reasons.
Usage and semantics of clangd --style=<string> should be identical to those of clang-format --style=<string>.
Issue also created on clangd repository: clangd/clangd#2397