20.04 firewall conundrum

I'm trying to share files on home network between two linux machines: host-A is Ubuntu 20.04, host-B is Red Hat. Samba worked well until distr. upgrade to 20.04. Now cifs mount from host-B reports "No route to host". Typical and obvious remedies don't work. sudo ufw status shows a bunch of ports allowed. I can ping host-A or ping ip of host-A, but cannot connect with gigolo or other smb protocol. Then I tried to set up nfs - same problem. Testing connection from host-B:

nmap host-A

returns 22 tcp open ssh but when I do

ssh host-A:22

I get " Could not resolve host... Name or service not known" Same with ip address instead of host name.

I know smb or nfs does not use port 22, the above is only to demonstrate that something in firewall is not working the way I understand it should.

I've searched answers but so far this remains a conundrum for me. I must be doing something wrong or missing something. To me it looks like my Ubuntu 20,04 (host-A) can only react to ping in my home network (wireless, 192.168.0.0).

CORRECTION: my test with ssh was incorrectly described. The correct command was ssh host-A, and host-A did in fact recognize the connection attempt, registered host-B. Then ssh user@host-A did connect after entering user password. Then I had terminal access to host-A on the host-B machine. Nevertheless, neither samba nor nfs file sharing succeeded despite having ports allowed in ufw. Same error as in my original posting.

ADDITIONAL info based on Answer 1: Outputs of host command on local network targeting Host-B

user@Host-A:~/Desktop$ host Host-B
Host Host-B not found: 2(SERVFAIL)
user@Host-A:~/Desktop$ host 192.168.nnn.mmm
mmm.nnn.168.192.in-addr.arpa domain name pointer Host-B.
user@Host-A:~/Desktop$

If I do vpn on Host-B where it is on mydomain.com

user@Host-A:~/Desktop$ host Host-B.mydomain.com
Host-B.mydomain.com has address xxx.pub.lic.ip
user@Host-A:~/Desktop$ 

Samba related command outputs:

user@Host-A:~/Desktop$ sudo smbstatus
[sudo] password for user: 

Samba version 4.11.6-Ubuntu
PID     Username     Group        Machine                                   Protocol Version  Encryption           Signing              
 ----------------------------------------------------------------------------------------------------------------------------------------

Service      pid     Machine       Connected at                     Encryption   Signing     
---------------------------------------------------------------------------------------------

No locked files

user@Host-A:~/Desktop$ findsmb

                            *=DMB
                            +=LMB
IP ADDR         NETBIOS NAME     WORKGROUP/OS/VERSION 
---------------------------------------------------------------------
user@Host-A:~/Desktop$ smbtree
user@Host-A:~/Desktop$ 

Same in Host-B [userB@Host-B Desktop]$ smbstatus

Samba version 3.6.23-53.el6_10
PID     Username      Group         Machine                        
-------------------------------------------------------------------

Service      pid     machine       Connected at
-------------------------------------------------------

No locked files

[userB@Host-B Desktop]$ findsmb

                                *=DMB
                                +=LMB
IP ADDR         NETBIOS NAME     WORKGROUP/OS/VERSION 
---------------------------------------------------------------------
192.168.nnn.mmm   CENTOS         [AB] [Unix] [Samba 3.6.23-53.el6_10]
[userB@Host-B Desktop]$ smbtree
Enter userB's password: 
[userB@Host-B Desktop]$

More info: Apparently Host-B finds itself in samba and Host-A does not. However, in Host-A (the Ubuntu machine) Browse Network in Thunar does display the netbios name of itself, defined in smb.conf. Yet findsmb command cannot find itself.