PS C:\Windows\system32> sfdx plugins:install @salesforce/lwc-dev-server
Successfully validated digital signature for @salesforce/lwc-dev-server.
Finished digital signature check.
warning @salesforce/lwc-dev-server > cpx > chokidar@1.7.0: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
warning @salesforce/lwc-dev-server > request-promise-native@1.0.9: request-promise-native has been deprecated because it extends the now deprecated request package, see https://github.com/request/request/issues/3142
warning @salesforce/lwc-dev-server > jsdom > request-promise-native@1.0.9: request-promise-native has been deprecated because it extends the now deprecated request package, see https://github.com/request/request/issues/3142
warning @salesforce/lwc-dev-server > cpx > chokidar > fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
warning @salesforce/lwc-dev-server > @webruntime/compiler > babel-eslint@10.1.0: babel-eslint is now @babel/eslint-parser. This package will no longer receive updates.
warning @salesforce/lwc-dev-server > @webruntime/compiler > rollup-plugin-commonjs@9.3.4: This package has been deprecated and is no longer maintained. Please use @rollup/plugin-commonjs.
warning @salesforce/lwc-dev-server > @webruntime/compiler > rollup-plugin-node-resolve@4.2.4: This package has been deprecated and is no longer maintained. Please use @rollup/plugin-node-resolve.
warning @salesforce/lwc-dev-server > @webruntime/compiler > rollup-plugin-replace@2.2.0: This module has moved and is now available at @rollup/plugin-replace. Please update your dependencies. This version is no longer maintained.
warning @salesforce/lwc-dev-server > @webruntime/api > @lwc/compiler > rollup-plugin-replace@2.2.0: This module has moved and is now available at @rollup/plugin-replace. Please update your dependencies. This version is no longer maintained.
warning @salesforce/lwc-dev-server > jsdom > request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
warning @salesforce/lwc-dev-server > @salesforce/core > jsforce > request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
warning @salesforce/lwc-dev-server > cpx > babel-runtime > core-js@2.6.12: core-js@<3 is no longer maintained and not recommended for usage due to the number of issues. Please, upgrade your dependencies to the actual version of core-js@3.
warning @salesforce/lwc-dev-server > jsdom > request > har-validator@5.1.5: this library is no longer supported
warning @salesforce/lwc-dev-server > cpx > chokidar > readdirp > micromatch > snapdragon > source-map-resolve > resolve-url@0.2.1: https://github.com/lydell/resolve-url#deprecated
warning @salesforce/lwc-dev-server > cpx > chokidar > readdirp > micromatch > snapdragon > source-map-resolve > urix@0.1.0: Please see https://github.com/lydell/urix#deprecated
warning "@salesforce/lwc-dev-server > request-promise-native@1.0.9" has unmet peer dependency "request@^2.34".
warning "@salesforce/lwc-dev-server > @rollup/plugin-alias@3.1.2" has unmet peer dependency "rollup@^1.20.0||^2.0.0".
warning "@salesforce/lwc-dev-server > request-promise-native > request-promise-core@1.1.4" has unmet peer dependency "request@^2.34".
error C:\Users\31622\AppData\Local\sfdx\node_modules\fibers: Command failed.
Exit code: 1
Command: node build.js || nodejs build.js
Arguments:
Directory: C:\Users\31622\AppData\Local\sfdx\node_modules\fibers
Output:
node-gyp not found! Please ensure node-gyp is in your PATH--
Try running: `sudo npm install -g node-gyp`
spawn node-gyp.cmd ENOENT
'nodejs' is not recognized as an internal or external command,
operable program or batch file.
Installing plugin @salesforce/lwc-dev-server... failed
    Error: yarn add @salesforce/lwc-dev-server@latest --non-interactive
    --mutex=file:C:\Users\31622\AppData\Local\sfdx\yarn.lock
    --preferred-cache-folder=C:\Users\31622\AppData\Local\sfdx\yarn --check-files exited with code 1

• Installled node-gyp
• Uninstalled node and npm.
• I checked the path and made sure node.js is there.

PS C:\Windows\system32> sfdx plugins:install @salesforce/lwc-dev-server
Successfully validated digital signature for @salesforce/lwc-dev-server.
Finished digital signature check.
warning @salesforce/lwc-dev-server > cpx > chokidar@1.7.0: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
warning @salesforce/lwc-dev-server > request-promise-native@1.0.9: request-promise-native has been deprecated because it extends the now deprecated request package, see https://github.com/request/request/issues/3142
warning @salesforce/lwc-dev-server > jsdom > request-promise-native@1.0.9: request-promise-native has been deprecated because it extends the now deprecated request package, see https://github.com/request/request/issues/3142
warning @salesforce/lwc-dev-server > cpx > chokidar > fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
warning @salesforce/lwc-dev-server > @webruntime/compiler > babel-eslint@10.1.0: babel-eslint is now @babel/eslint-parser. This package will no longer receive updates.
warning @salesforce/lwc-dev-server > @webruntime/compiler > rollup-plugin-commonjs@9.3.4: This package has been deprecated and is no longer maintained. Please use @rollup/plugin-commonjs.
warning @salesforce/lwc-dev-server > @webruntime/compiler > rollup-plugin-node-resolve@4.2.4: This package has been deprecated and is no longer maintained. Please use @rollup/plugin-node-resolve.
warning @salesforce/lwc-dev-server > @webruntime/compiler > rollup-plugin-replace@2.2.0: This module has moved and is now available at @rollup/plugin-replace. Please update your dependencies. This version is no longer maintained.
warning @salesforce/lwc-dev-server > @webruntime/api > @lwc/compiler > rollup-plugin-replace@2.2.0: This module has moved and is now available at @rollup/plugin-replace. Please update your dependencies. This version is no longer maintained.
warning @salesforce/lwc-dev-server > jsdom > request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
warning @salesforce/lwc-dev-server > @salesforce/core > jsforce > request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
warning @salesforce/lwc-dev-server > cpx > babel-runtime > core-js@2.6.12: core-js@<3 is no longer maintained and not recommended for usage due to the number of issues. Please, upgrade your dependencies to the actual version of core-js@3.
warning @salesforce/lwc-dev-server > jsdom > request > har-validator@5.1.5: this library is no longer supported
warning @salesforce/lwc-dev-server > cpx > chokidar > readdirp > micromatch > snapdragon > source-map-resolve > resolve-url@0.2.1: https://github.com/lydell/resolve-url#deprecated
warning @salesforce/lwc-dev-server > cpx > chokidar > readdirp > micromatch > snapdragon > source-map-resolve > urix@0.1.0: Please see https://github.com/lydell/urix#deprecated
warning "@salesforce/lwc-dev-server > request-promise-native@1.0.9" has unmet peer dependency "request@^2.34".
warning "@salesforce/lwc-dev-server > @rollup/plugin-alias@3.1.2" has unmet peer dependency "rollup@^1.20.0||^2.0.0".
warning "@salesforce/lwc-dev-server > request-promise-native > request-promise-core@1.1.4" has unmet peer dependency "request@^2.34".
error C:\Users\31622\AppData\Local\sfdx\node_modules\fibers: Command failed.
Exit code: 1
Command: node build.js || nodejs build.js
Arguments:
Directory: C:\Users\31622\AppData\Local\sfdx\node_modules\fibers
Output:
node-gyp not found! Please ensure node-gyp is in your PATH--
Try running: `sudo npm install -g node-gyp`
spawn node-gyp.cmd ENOENT
'nodejs' is not recognized as an internal or external command,
operable program or batch file.
Installing plugin @salesforce/lwc-dev-server... failed
    Error: yarn add @salesforce/lwc-dev-server@latest --non-interactive
    --mutex=file:C:\Users\31622\AppData\Local\sfdx\yarn.lock
    --preferred-cache-folder=C:\Users\31622\AppData\Local\sfdx\yarn --check-files exited with code 1

• Installled node-gyp
• Uninstalled node and npm.
• I checked the path and made sure node.js is there.