Zero nyc coverage on Next server tested using Playwright

Question

I'm trying to get test coverage using Playwright on a Next server. The tests reside in e2e-tests/ and the server in frontend/.

After some struggles I've managed to end up some json files looking like the following inside e2e-tests/.nyc_output:

{
    "/[path]/Component.tsx": {
      "path": "/[path]/Component.tsx",
      "all": false,
      "statementMap": {
        "0": { "start": { "line": 1, "column": 0 }, "end": { "line": 1, "column": 45 } },
        "1": { "start": { "line": 2, "column": 0 }, "end": { "line": 2, "column": 37 } },
        ...
      },
      "s": {
        "0": 1,
        "1": 1,
        ...
      },
      "branchMap": {
        "0": {
          "type": "branch",
          "line": 14,
          "loc": { "start": { "line": 14, "column": 0 }, "end": { "line": 36, "column": 1 } },
          "locations": [{ "start": { "line": 14, "column": 0 }, "end": { "line": 36, "column": 1 } }]
        },
        ...
      },
      "b": { "0": [6] ... },
      "fnMap": {
        "0": {
          "name": "Component",
          "decl": { "start": { "line": 14, "column": 0 }, "end": { "line": 36, "column": 1 } },
          "loc": { "start": { "line": 14, "column": 0 }, "end": { "line": 36, "column": 1 } },
          "line": 14
        },
        ...
      },
      "f": { "0": 6, ... }
    }
  }

I'm not sure how to read these files, but it looks to me like there is some coverage. But when I then run

npx nyc report --all --cwd ".." --include "**/frontend/**" --nycrc-path e2e-tests/.nycrc

where .nycrc is

{
  "extends": "nyc-config-tsx",
  "all": true
}

the output shows zero coverage:

-------------------------|---------|----------|---------|---------|-------------------
File                     | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
-------------------------|---------|----------|---------|---------|-------------------
All files                |       0 |        0 |       0 |       0 |
  Component.tsx          |       0 |        0 |       0 |       0 | 15-48
  ...                    |       0 |        0 |       0 |       0 | 

I suspect it has something to do with paths. Do I have to specify how the results in the json files correspond to their source files somehow?