According to the release notes of Samba 4.11(https://www.samba.org/samba/history/samba-4.11.0.html) there is a strong requirement to keep SMB1 support for old DOS application and LANMAN compatibility.
Necessary settings to keep it running:
lanman auth = yes
encrypt passwords = yes
server min protocol = LANMAN1
client min protocol = LANMAN1
So please keep the SMB1 support to support DOS LANMAN clients.
Eventually the SMB1 server code inside Samba is going to have to be removed if we want to make progress on the SMB2+ interfaces.
At that point we will freeze a version of Samba that you will be able to use with SMB1 for old DOS applications.
*** Bug 14197 has been marked as a duplicate of this bug. ***