Configure Samba for Windows 3.1
Before you begin, you should know that SMB1 is very insecure. Only do this on a Samba server that is only accessible locally and not accessible from the internet. Also, an SMB account should already be set up in Samba using smbpasswd.
Compatibility
SMB1 support was deprecated in Samba 4.11.0 (2019-09-17)[1] as part of the effort to rewrite the VFS layer so that file operations are performed using openat-style system calls instead of paths. This effort was completed in Samba 4.15.0 (2021-09-20)[2].
Samba 4.16.0 (still in development)[3] is the first post-deprecation version to remove SMB1 features; wildcards in the copy, rename, and delete commands sent by DOS-based Windows clients (such as 3.1) are not supported.
If further removals happen, I might fork 4.10.0, 4.11.0, or 4.15.0, and rip out anything unrelated to SMB1 support, try to apply any applicable patches from future versions, and maybe call it something like smb1d.
Instructions
Edit /etc/samba/smb.conf and make sure the following lines exist:
[global]
client min protocol = CORE
server min protocol = CORE
client plaintext auth = yes
Then, systemctl reload smbd.service.
