Firefox 140.3.1esr (32-bit) – Getting a PR_CONNECT_RESET_ERROR but Chrome works okay on the same site. How to adjust Firefox settings properly?

I have two machines (Windows 10 and Windows 11) with Firefox 140.3.1esr (32-bit) installed which shows the same failure when I enter one site’s (urban3p.com) URL:

PR_CONNECT_RESET_ERROR

screen in Firefox

Chrome at the same machines goes at this URL without any failures.

Any ideas what to change in about:config in Firefox to allow it opening this URL without such an error?