To crunch the project, you add it, doing so asks for the url of the project. That is normally on the front page, but it is not there. What url does BOINC Manager want me to put there?

Hello! :)
Project URL is http://188.68.219.141/sidocktest/ , you can use it in BOINC Manager.

Project is running now.

Also see this thread as well adrianxw: https://fightcovid.boinc.ru/sidocktest/forum_thread.php?id=16
The changed the IP address to a new URL with top-level domain .ru by now.

A little odd. On this machine, the work units come, crunch for a little over an hour and return, they are verified and credited. I added the project to the other, almost identical, computer under my desk. On that machine, units arrive, crunch for, typically, 10 seconds and return. They show as failed. The log does not show any error message. I've suspended the project on there.

195 (0x000000C3) EXIT_CHILD_FAILED

Hi! :) Microsoft Visual C++ Redistributable for Visual Studio 2019 installed on both computers?

Thats a good point, I'd rebuilt that SSD recently, might have left it out.

... and it's running, me stupid. Good call.