Hello @wojtekcz
Also from me a big thank you for this guide! I tried following your guide, but got stuck and hoped that you could help me out? It seems that I was able to successfully execute the instructions of “demo_colab_ssh_access”. Because when I run the cell with
# ssh tunnel to portmap.io

options = '-oStrictHostKeyChecking=no -oUserKnownHostsFile=/dev/null'

!ssh $options -i $fn_private_key_pem -f -R 53525:localhost:22 wojtekcz.first@wojtekcz-53525.portmap.io -N

, I get as output
Warning: Permanently added 'wojtekcz-53525.portmap.io,<three digits>.<three digits>.<three digits>.<two digits>' (ECDSA) to the list of known hosts., which I take as it having worked successfully!
(of course, I have replaced “53525”, “wojtekcz” and “first” appropriately, as well as the value for “fn_private_key_pem”)
The next step in your guide was to follow “configuring remote interpreter via ssh in PyCharm” and this is where I got stuck. I tried the “New server configuration” option with <three digits>.<three digits>.<three digits>.<two digits> as my Host, 22 as port and wojtekcz-53525.portmap.io as my username. As my authentication option, I picked “Key pair (OpenSSH or PuTTY):” with my “private_key_pem”, but got
Connection to wojtekcz-53525.portmap.io@<three digits>.<three digits>.<three digits>.<two digits>:22 failed:

Timeout expired

as an error. And thus, I have been scratching my head what I am doing wrong.