A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
I have tested with two domains, and these two domains are both can check out and open in desktop app.
In the SharePoint online, if users are authenticating via one-time passcode when they don't already have a work or school account or a Microsoft account, then they do not have a real AAD account and thus cannot check out and open in desktop app.
To troubleshoot this issue, here are two tips:
1.Go to Microsoft 365 admin center -> Users -> Guest users -> Add a guest user.
2.Open SharePoint Online Management Shell as administrator, run Set-SPOTenant -EnableAzureADB2BIntegration $true
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