[SalesForce] ERROR running force:source:pull: Entity of type ‘Workflow’ named ‘Workflow’ cannot be found

I'll answer as I did find some kind of workaround

Those steps allow me to work DX-style with Managed Package, Namespace and Person Account

1 Create scratch org WITHOUT Namespace, using flag -n, --nonamespace

sfdx force:org:create -f config/project-scratch-def.json -a ScratchNONameSpace -s -n

2 First thing is to pull Account.Business_Account, which works as expected

$ sfdx force:source:status -r

=== Source Status
STATE       FULL NAME                 TYPE        PROJECT PATH
Remote Add  Account.Business_Account  RecordType

$ sfdx force:source:pull

=== Pulled SourceSTATE  FULL NAME                 TYPE        PROJECT PATH
Add    Account.Business_Account  RecordType  force-app/main/default/objects/Account/recordTypes/Business_Account.recordType-meta.xml

3 Create scratch org WITH Namespace

sfdx force:org:create -f config/project-scratch-def.json -a ScratchWithNameSpace -s

4 Check status, you'll see conflicts

$ sfdx force:source:status
=== Source Status
STATE                      FULL NAME                 TYPE        PROJECT PATH

Local Add (Conflict)       Account.Business_Account  RecordType  force-app/main/default/objects/Account/recordTypes/Business_Account.recordType-meta.xml
Remote Changed (Conflict)  Account.Business_Account  RecordType  force-app/main/default/objects/Account/recordTypes/Business_Account.recordType-meta.xml

5 Push your code using flag -f, --forceoverwrite

$ sfdx force:source:push -f
=== Pushed Source
STATE  FULL NAME                 TYPE        PROJECT PATH

Add    Account.Business_Account  RecordType  force-app/main/default/objects/Account/recordTypes/Business_Account.recordType-meta.xml

$ sfdx force:source:status
=== Source Status
No results found

After that you would be able to push/pull without issues.

When you enable the org-wide setting in the Dev Hub menu, the only user profile that will have the permission enabled is the default Sys Admin profile. If you use another profile in production, you need to grant the "Create and Update Second-Generation Packages" permission for the profile being used or otherwise add the permission to yourself.

I was stuck myself, but found this article to help: https://developer.salesforce.com/docs/atlas.en-us.sfdx_dev.meta/sfdx_dev/sfdx_dev_dev2gp_before.htm

You'll likely also want to give yourself/profile the "Promote a package version to released" permission.