Over time the defaults of smb.conf have changed to where they no longer automatically support the older protocol versions and authentication methods of NT/9x/etc., but here's the secret to getting it to work (until they finally remove support):

In the [global] section of smb.conf, add:

server min protocol = NT1

lanman auth = yes

ntlm auth = yes

Then re-generate your SMB passwords. NTLM auth is used by NT and above clients, and LANMAN auth is needed for 9x and DOS.

https://askubuntu.com/questions/1213759/allow-smb-1-with-lan...