I haven't been able to reproduce your issue. I followed the steps by @jose in the thread you linked in a previous post and I was able to properly enable and install Multisite on a regular WordPress site. The only modification I needed to do to his guide was setting my instance IP address for the
SITEURL values in the database as I'm using a cloud image instead of my local computer and the value that WordPress generates for these parameters is
127.0.0.1 by default.
As you can see in the image above, I added a new WordPress site at
IP-ADDRESS/wp2 and I see the "Plugins" button.
I also see that you have some custom plugins such as Avada and others. Can you try using a fresh new instance without adding those plugins? Also please run the bnsupport tool that was mentioned previously, it will help us to debug your issue.
Alternatively, we have a Bitnami WordPress Multisite solution that you can find in the link below. Can you try using this instead of converting a regular WordPress into multisite?