ssh tunnelling testing

[Gary Dale <gary@extremeground.com>]

I'm running Debian/Buster on various servers, including my home server. 
I'm trying to set up an ssh tunnel that I can use post-pandemic in case 
I need to access my home network remotely. I'm already doing this to 
various remote servers so I thought this should just work, since I can 
already access my home server locally using its 192.168... address 
(actually through the /etc/hosts file using the server's name).

I've set up port forwarding on both my routers (I have an inner network 
and an outer one, using the outer network for devices I don't really 
control). I can access my Apache2 server on the inner network by 
forwarding port 80 on the outer network to the WAN address of the inner 
router and forwarding that to my server. Pointing my browser to the 
external IP address of the outer router brings up the default page - 
which I can change so I know it's the actual local page.

However, when I try to ssh to the same address, it just times out.

I've compared the sshd.conf file on my local server to one on a remote 
server and they are identical. The only uncommented lines are:

PasswordAuthentication no
ChallengeResponseAuthentication no
UsePAM yes
X11Forwarding yes
PrintMotd no
AcceptEnv LANG LC_*
Subsystem       sftp    /usr/lib/openssh/sftp-server


Any ideas on what's going wrong?