So, I checked my node again.
It's not needed with my guide, since I simply don't use
CookieAuthentication.
Instead, I have these more compact, readable 3-liners for each service. In my opinion easier to understand what's going on, modify if needed and less modifications to the system.
[2] Create another Tor hidden service for C-Lightning. Similar procedure as before.
[3] Below the other hidden service, add this info for Lightning.
HiddenServiceDir /var/lib/tor/lightningd_hidden_service/
HiddenServiceVersion 3
HiddenServicePort 9735 127.0.0.1:9735
The official C-Lightning guide would have you do:
ControlPort 9051
CookieAuthentication 1
CookieAuthFileGroupReadable 1
You also need to make your user a member of the Tor group.
If it's somehow possible to avoid opening any type of port and changing any types of permissions, I usually avoid it.