Thank you very much for your reply, have a nice day)
Hello @aarrttyyrr,
My name is Alejandra, and I am happy to assist with your inquiry and appreciate you contacting LastPass Support!
I hope this message finds you well. You can add any user to your account it doesn't matter they are not using the same domain. The only problem will be if you use an active directory to add your users but if this are manual invitations there will not be any problem.
Kind Regards,
Alejandra
LastPass Tech Support