Startup: `radian: error: no such option: --slave`

During startup in a remote session with {languageserver 0.3.4} and `radian` 0.4.7 I get

```
Usage: radian

radian: error: no such option: --slave

Language server exited with exit code 2
```

I have `r.lsp.debug` to TRUE but cannot track it down further. 

`rterm`  is set to `~/.local/bin/radian`.

Any ideas from your side what might be the problem?