root@localhost-app:/# discourse disable_readonly
The site is now fully operable.
Here I did your instruction:
root@localhost:/var/discourse# ./launcher enter app
WARNING: No swap limit support
root@localhost-app:/# rails c
[1] pry(main)> Discourse.disable_readonly_mode
=> true
root@localhost-app:/# discourse enable_readonly
The site is now in readonly mode.
root@localhost-app:/# discourse disable_readonly
The site is now fully operable.
root@localhost-app:/#
But it seems it only affects on the first site, not the second site.
(For more info: I configured multisite, and I restored with backup data. Then it happened)