Getting multiple errors when running "yarn start"

I ran yarn install successfully
I then ran yarn start
After that, I was immediately thrown with multiple errors
I am unsure if this is a specific problem with Specimen Builder. Perhaps this is related to Yarn/Webpack/Eleventy instead. The output is below:
C:\Users\frede\Downloads\specimen-builder>yarn start
yarn run v1.22.15
warning ..\..\package.json: No license field
$ cross-env NODE_ENV=development ELEVENTY_ENV=development npm-run-all clean build:webpack --parallel start:*
warning ..\..\package.json: No license field
$ rimraf ./_site
warning ..\..\package.json: No license field
$ webpack
Browserslist: caniuse-lite is outdated. Please run:
npx browserslist@latest --update-db
Hash: 3f10d895e96be93fcfac
Version: webpack 4.44.0
Time: 6237ms
Built at: 18/01/2022 7:59:53 pm
                                                            Asset       Size  Chunks                         Chunk Names
                          ..\src\_includes\.webpack\manifest.json  517 bytes          [emitted]
      fonts/STIX2Text-Bold.cbe5baa62c07ac0e7e5809552734238b.woff2    117 KiB          [emitted]
fonts/STIX2Text-BoldItalic.d8ea231671919371fbff357fe06452c3.woff2    123 KiB          [emitted]
    fonts/STIX2Text-Italic.925bcb98c371de1527af31fa1ac5bfa7.woff2    121 KiB          [emitted]
   fonts/STIX2Text-Regular.3d11ae4eadf760794ef95d4b33e1d5ab.woff2    117 KiB          [emitted]
                                     main.3f10d895e96be93fcfac.js   17.3 KiB    main  [emitted] [immutable]  main
                                  styles.45159fc4850cf5ffb141.css   14.5 KiB    main  [emitted] [immutable]  main
Entrypoint main = styles.45159fc4850cf5ffb141.css main.3f10d895e96be93fcfac.js
[0] multi ./src/js/main.js ./src/css/main.css 40 bytes {main} [built]
[./src/_data/fontdata.json] 395 bytes {main} [built]
[./src/css/main.css] 39 bytes {main} [built]
[./src/img sync recursive \.(png|jpg|svg)$] ./src/img ?external sync \.(png|jpg|svg)$ 160 bytes {main} [built]
[./src/js/assets.js] 200 bytes {main} [built]
[./src/js/main.js] 4.68 KiB {main} [built]
    + 2 hidden modules
Child mini-css-extract-plugin node_modules/css-loader/dist/cjs.js!node_modules/postcss-loader/src/index.js!src/css/main.css:
    Entrypoint mini-css-extract-plugin = *
    [./node_modules/css-loader/dist/cjs.js!./node_modules/postcss-loader/src/index.js!./src/css/main.css] ./node_modules/css-loader/dist/cjs.js!./node_modules/postcss-loader/src!./src/css/main.css 16.8 KiB {mini-css-extract-plugin} [built]
    [./src/fonts/STIX2Text-Bold.woff2] 103 bytes {mini-css-extract-plugin} [built]
    [./src/fonts/STIX2Text-BoldItalic.woff2] 109 bytes {mini-css-extract-plugin} [built]
    [./src/fonts/STIX2Text-Italic.woff2] 105 bytes {mini-css-extract-plugin} [built]
    [./src/fonts/STIX2Text-Regular.woff2] 106 bytes {mini-css-extract-plugin} [built]
        + 2 hidden modules
warning ..\..\package.json: No license field
warning ..\..\package.json: No license field
$ webpack -w
$ eleventy --serve

webpack is watching the files…

Error writing templates: (more in DEBUG output)
> Having trouble writing template: _site/index.html

`TemplateWriterWriteError` was thrown
> Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json., file:src/_layouts/default.html, line:16

`RenderError` was thrown
> Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json.

`Error` was thrown:
    Error: Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json.
        at webpackAssetPath (C:\Users\frede\Downloads\specimen-builder\.eleventy.js:17:9)
Problem writing Eleventy templates: (more in DEBUG output)
> Having trouble writing template: _site/index.html

`TemplateWriterWriteError` was thrown
> Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json., file:src/_layouts/default.html, line:16

`RenderError` was thrown
> Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json.

`Error` was thrown:
    Error: Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json.
        at webpackAssetPath (C:\Users\frede\Downloads\specimen-builder\.eleventy.js:17:9)
Processed 0 files in 1.46 seconds (v0.9.0)
Watching…
[Browsersync] Access URLs:
 -------------------------------------
       Local: http://localhost:8080
    External: http://192.168.59.1:8080
 -------------------------------------
          UI: http://localhost:3001
 UI External: http://localhost:3001
 -------------------------------------
[Browsersync] Serving files from: _site
Browserslist: caniuse-lite is outdated. Please run:
npx browserslist@latest --update-db
File changed: src\_includes\.webpack\manifest.json
Hash: 3f10d895e96be93fcfac
Version: webpack 4.44.0
Time: 8389ms
Built at: 18/01/2022 8:00:08 pm
                                                            Asset       Size  Chunks                         Chunk Names
                          ..\src\_includes\.webpack\manifest.json  517 bytes          [emitted]
      fonts/STIX2Text-Bold.cbe5baa62c07ac0e7e5809552734238b.woff2    117 KiB          [emitted]
fonts/STIX2Text-BoldItalic.d8ea231671919371fbff357fe06452c3.woff2    123 KiB          [emitted]
    fonts/STIX2Text-Italic.925bcb98c371de1527af31fa1ac5bfa7.woff2    121 KiB          [emitted]
   fonts/STIX2Text-Regular.3d11ae4eadf760794ef95d4b33e1d5ab.woff2    117 KiB          [emitted]
                                     main.3f10d895e96be93fcfac.js   17.3 KiB    main  [emitted] [immutable]  main
                                  styles.45159fc4850cf5ffb141.css   14.5 KiB    main  [emitted] [immutable]  main
Entrypoint main = styles.45159fc4850cf5ffb141.css main.3f10d895e96be93fcfac.js
[0] multi ./src/js/main.js ./src/css/main.css 40 bytes {main} [built]
[./src/_data/fontdata.json] 395 bytes {main} [built]
[./src/css/main.css] 39 bytes {main} [built]
[./src/img sync recursive \.(png|jpg|svg)$] ./src/img ?external sync \.(png|jpg|svg)$ 160 bytes {main} [built]
[./src/js/assets.js] 200 bytes {main} [built]
[./src/js/main.js] 4.68 KiB {main} [built]
    + 2 hidden modules
Child mini-css-extract-plugin node_modules/css-loader/dist/cjs.js!node_modules/postcss-loader/src/index.js!src/css/main.css:
    Entrypoint mini-css-extract-plugin = *
    [./node_modules/css-loader/dist/cjs.js!./node_modules/postcss-loader/src/index.js!./src/css/main.css] ./node_modules/css-loader/dist/cjs.js!./node_modules/postcss-loader/src!./src/css/main.css 16.8 KiB {mini-css-extract-plugin} [built]
    [./src/fonts/STIX2Text-Bold.woff2] 103 bytes {mini-css-extract-plugin} [built]
    [./src/fonts/STIX2Text-BoldItalic.woff2] 109 bytes {mini-css-extract-plugin} [built]
    [./src/fonts/STIX2Text-Italic.woff2] 105 bytes {mini-css-extract-plugin} [built]
    [./src/fonts/STIX2Text-Regular.woff2] 106 bytes {mini-css-extract-plugin} [built]
        + 2 hidden modules
Error writing templates: (more in DEBUG output)
> Having trouble writing template: _site/index.html

`TemplateWriterWriteError` was thrown
> Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json., file:src/_layouts/default.html, line:16

`RenderError` was thrown
> Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json.

`Error` was thrown:
    Error: Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json.
        at webpackAssetPath (C:\Users\frede\Downloads\specimen-builder\.eleventy.js:17:9)
Problem writing Eleventy templates: (more in DEBUG output)
> Having trouble writing template: _site/index.html

`TemplateWriterWriteError` was thrown
> Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json., file:src/_layouts/default.html, line:16

`RenderError` was thrown
> Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json.

`Error` was thrown:
    Error: Unknown Webpack asset requested: css\main.css. Check .webpack/manifest.json.
        at webpackAssetPath (C:\Users\frede\Downloads\specimen-builder\.eleventy.js:17:9)
Processed 0 files in 0.38 seconds (v0.9.0)
Watching…
[Browsersync] Reloading Browsers...
markboulton / specimen-builder

Getting multiple errors when running "yarn start" #42
