Well i can tell it is not at all
I use a LG OLED with the Plex preview, 3 x ipad, iMac. No real issues.
explain yours please
I mean, I am sure my server works as it should, and the issue is related to the Plex App on my Mac… Might be a problem with my Mac, not with the Plex for Mac, but still. I have no idea how to fix this.
Ok, do you still have the installer, or even better today a update has been released. Can you Expand the new installer. Then we will go threw the issues
I already tried todays update, but to follow your request to the t. I redownloaded it. unzipped the file, dragged the Plex App to the Applications folder and opened it. Indeed it ask permission as discussed, the first time its opened.

I click open, icon bounces around for a minute or so. Then stops bouncing and all I can do is force quit

Great, now were getting some where
Go to system Pref/ Security & Privacy/ Unlock with your admin password
Ok, to do what?
Now your there, if your in General/ you will find a Allow/ click that allow and try to open again
Plex seems to be a identified developer so all I have to do is click open

Just to make sure, I understand what you want me to do, I have done that many times, I know how that part works when you download an app from an unknown internet source. That is not what is blocking me here.
Ok something wrong s it works correct for me
Just for arguments sake and cause solutions are sometimes where you dont expect them to be. I changed my setting to App Store. Deleted the App again, unzipped it, dragged it opened it. It will indeed force me to go into Settings like you said and specifically give permission. Which I then did, brings me to the same point… Plex Icon bouncing up and down with nothing happening.
Yeah… My friend has no issues with it either, running Mac Os as well.
I did not download from apple but from plex
Same here, downloaded from Plex website: https://www.plex.tv/media-server-downloads/#plex-app
NO AV, or similar. NO VPN running
Nope, plus the only issue that could cause, is the app not connecting directly (or at all) to the server. Something is messed up, preventing Plex app from installing properly, but again, no idea what.
Your opening from a dock icon or from app
I believe your 32400 port is not open
Check via network app, search in spotlight for network app
Isnt a dock icon just a link to an app?
Plex.tv webbased app shows no issues with ports of the server

