First thing: you can play Prison Architect without Internet and without an Account on Paradox - don't feel forced to do it!
But if you don't want to be tracked/spied/get your disk polluted with launchers, directly change start.sh after installing it
via offline installer (see the end of this post).

When I first got an eye to "Prison Architect" I saw the negative reviews and asked GOG support (04. March 2020)
about DRM via the launcher.
The responce was:
"The Prison Architect case is a big misunderstanding or wilful ignorance when it comes to the Paradox Launcher.
  It is not DRM in any way, the game can be started without the launcher, there is a separate executable for it.
  Even if you start the Launcher no login or even internet connection is required."

So I bought the game, get it via offline installer for Linux, installed it and - no launcher, no DRM, disconnecting
from Internet and it worked. I was angry about the wrong comments and made a good review stating the facts.

But this was just just temporary tactics - and I am sorry to think that the commenters gave wrong statements.
As this launcher got invoked by start.sh since 23. Feb. 2021 (the_glasshouse_5249_44985) and is
till the current version of a few hours ago - 08. April 2021 (5590 46186) part of the GOG installer creating start.sh.

Well, the point about no Internet connection necessary to play may be still valid, but this really IS DRM
what Paradox does:

1) Suddenly without noting the launcher is invoked by the start.sh script - after several updates being fine I would
    never have expected they will use it again ... nasty job well done.
2) The launcher must have connected to Paradox - and without notice installed another installer on my machine.
3) After looking (I have 2 Paradox games under Linux) I had more than two Paradox launchers spread over the file system tree - not part of the typical gaming directories.
4) I would have asked Paradox about a statement: why the sudden come back of a nasty DRM technique on GOG, why the proliferation of Paradox launchers around FS, what data are exchanged via launchers, ... what about Linux port of Teleglitch on GOG, ... - but you must have a Paradox account to open a ticket - no mail sufficient to open a ticket.
Yes, this is the worst DRM I have seen today. And not being a legal expert I am pretty sure that this is not legal -
at least in Europe (having worked more than 10 year as Unix specialist in IT business).

For those who want to play under Linux one can use Prison Architect and call it via start.sh after changing the line
   ./"Launcher/dowser"
to the correct one directly invoking the game:
   ./PrisonArchitect
And of cause the launcher does a good job in giving the impression that a Paradox account is necessary.
But this is still not the case.

Everyone may have criteria about a good game - for me the three games of Paradox are more than enough.
I would let my review get deleted, but as the tickets seem to be no longer worked on by GOG this will not happen
in near future. But I think that this forum post will clear the situation ... and you can make the game DRM free
while it is not in that form GOG is currently packaging it. And everyone can reflect upon what DRM means and
what definition will apply in this case.
If this is not DRM then there may be no DRM at all in the SW/HW world at all - and I don't think so.
DRM/espionage/tracking is technically the same ... one can not have one without the others and no one knows
what flavor of functionality is used and how this may change in future.
Same applies to the gaming clients around. Be free to use one - but understand what may result from that usage.
When something can be automatically updated - it can be automatically deleted or altered in any way! Just a matter of fact!

Hope this helps in clarifying this confused situation!