The approach that has worked for me so far is this:
git rebase origin/master
When the first conflict arises, I checkout the yarn.lock then re-perform the installation
git checkout origin/master -- yarn.lock
yarn install
This generates a new yarn.lock based on the origin/master version of yarn.lock, but including the changes I made to my package.json. Then it's just a matter of:
git add yarn.lock
git rebase --continue
And I'm back in business.