Shiny app authentication with multiple users

I have shiny running on Ubuntu (20.04), apache2 server. it was working, I had added three users to an app somehow. when I added a new user, I could not get the person authenticated. I then started reading a bunch of advice, which led to everything breaking with invalid callback URL messages. and also messages such as this “OpenID Connect Redirect URI with no parameters”

I am right now following the recommendations of this site

it is not clear if this is old instructions or the latest.

I also tried instructions given here

Is there gold-standard list of things to do to get get things working with some concrete examples. at this point I am confused about what the callback URL is supposed to be.

this should not be so difficult. tempted to just get rid of the authentication and maybe cobble something together some other way.

it is just frustrating that there is no clear timestamped guide (so I know I am not doing something outdated from 1905).

It seems like my use-case is not out on the bleeding edge by any means.

sorry, this seems like a great solution when it worked, but now, after many hours of struggles, I feel like I am out of my depth