Removed all the entries referencing uslug (assuming that was the correct thing to do) and it still failed in the same way.

"@joplin/fork-uslug@^1.0.4, @joplin/fork-uslug@workspace:packages/fork-uslug":
  version: 0.0.0-use.local
  resolution: "@joplin/fork-uslug@workspace:packages/fork-uslug"
  dependencies:
    node-emoji: 1.11.0
    should: ">= 0.2.1"
    unorm: ">= 1.0.0"
  languageName: unknown
  linkType: soft
"@joplin/lib@^2.6.3, @joplin/lib@workspace:packages/lib, @joplin/lib@~2.7":
  version: 0.0.0-use.local
  resolution: "@joplin/lib@workspace:packages/lib"
  dependencies:
...
    "@joplin/fork-uslug": ^1.0.4
"@joplin/renderer@^2.6.3, @joplin/renderer@workspace:packages/renderer, @joplin/renderer@~2.7":
  version: 0.0.0-use.local
  resolution: "@joplin/renderer@workspace:packages/renderer"
  dependencies:
...
    "@joplin/fork-uslug": ^1.0.4

Also removed the ones referencing https://github.com/laurent22/uslug, those ones didn't return to the lock file after I removed them and re-ran yarn install