Always-on On multi-domain cluster.

I have read the following link about creating multi-domain cluster and use always-on

https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/domain-independent-availability-groups?view=sql-server-ver15

and there is line like in the following :

FSW can't be use:

Kerberos can't be used :

1. it's means I can't create a file share folder for the witness?

2. And the login authen with SQL server method will all using NTLM ???????

Anyone try these limitation with creating multi-domain always-on ?