I finally found the solution to the issue on the GOG.com forums. Nothing obvious like setting admin privileges helped.
No, it’s more insidious.
Apparently when you go to regional settings, both the “Country or Region” and the “Regional Format” values must match the country.
I’ve had these set to “Ireland” + “English (Europe)”. Before this, I likely had it set to “Ireland” + “Croatian (Croatia)”.
Changing the values to “Ireland” + “English (Ireland)” resolved the issue.
I can finally play the game years after buying it. This was done on Windows 10 1903 (build 18362.10012).