I have to thank you OP for this info and testing by yourself and every member involved in this thread.
I am one of the lucky ones that has a Galaxy watch 5 pro with no Google Assistant due to issues in the app connection to the phone.
It goes to open the Google app to start activating assistant like it does with the 44mm Galaxy Watch 5, but it fails to go to the next step of activation and lands on the discovery page.
Well knowing how well this threads info worked for us on the Galaxy Watch 4, I have gone ahead and installed the Google Assistant Go version listed in the post using Bugjaeger.
This time we go into the watch settings >> about watch >> software info >> keep clicking the software version until it tells you developer mode ON.
Then goto watch settings >> Developer Options >> 1. turn on adb debugging
Then goto watch settings >> Developer Options >> 2. debug over wireless
Then goto watch settings >> Developer Options >> Wireless debugging >> + pair new deveice
In Bugjaeger we then start up the connection and click pair, enter the IP, the port and the passcode.
At this point it will be connected in Bugjaeger and the watch will beep showing a new notification for debugging.
Install the Google Assistant GO apk and voila you are good to go.
I did have to do an interactive shell to "wm density 280" in order to click the continue button for activation.
Remember to reset your density to its original number(which on the 5 pro is 340)
If you are like me and need assistant or the device gets returned, use this as a solution until google fixes their routine for activating assistant.
Feel good moment since I wont be returning this loved watch 5 pro!
EDIT1: Nothing above was editing only this addition,
I have also found that the workaround method for the BP/EKG by Dante is still working with the Galaxy Watch 5 Pro. Installation of his APK for the watch can be installed with Bugjaeger just like we installed Google Assistant Go just above.