/etc/samba/smb.conf

[global]
# Basic Samba configuration
server role = standalone server
passdb backend = tdbsam
obey pam restrictions = yes
security = user
printcap name = /dev/null
load printers = no
socket options = TCP_NODELAY IPTOS_LOWDELAY SO_RCVBUF=524288 SO_SNDBUF=524288
server string = Samba Server %v
map to guest = bad user
dns proxy = no
wide links = yes
follow symlinks = yes
unix extensions = no
acl allow execute always = yes
log file = /var/log/samba/%m.log
max log size = 1000
guest ok = no
read only = no

valid users = @shareaccess
# username map = /etc/samba/users.map
passdb backend = tdbsam:/etc/samba/passdb.tdb

# Security
client ipc max protocol = default
client max protocol = default
server max protocol = SMB3

client ipc min protocol = default
client min protocol = CORE
server min protocol = SMB2

# Special configuration for Apple's Time Machine
# fruit:model = Laptop
fruit:model = RackMac
fruit:advertise_fullsync = true
fruit:aapl = yes

## Definde your shares here
[TimeMachine Home]
path = /mnt/share/%U
valid users = %U
writable = yes
durable handles = yes
kernel oplocks = no
kernel share modes = no
posix locking = no
vfs objects = catia fruit streams_xattr
ea support = yes
browseable = yes
read only = No
inherit acls = yes
fruit:time machine = yes
spotlight = yes

/etc/avahi/services/timemachine.service

<?xml version="1.0" standalone='no'?>
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
 <name replace-wildcards="yes">%h</name>
 <service>
   <type>_smb._tcp</type>
   <port>445</port>
 </service>
 <service>
   <type>_device-info._tcp</type>
   <port>0</port>
   <txt-record>model=RackMac</txt-record>
 </service>
 <service>
   <type>_adisk._tcp</type>
   <txt-record>sys=waMa=0,adVF=0x100</txt-record>
   <txt-record>dk0=adVN=TimeMachine Home,adVF=0x82</txt-record>
 </service>
</service-group>

1. Create group 'shareaccess' and add users to the group
2. Create samba user password:

   smbpasswd -a michele

* Configuring Time Machine compatible Samba shares on Debian 10 Buster