Hi there,
Thank you for following the template. Sorry for the slow reply, I am on a bit of a development break at the moment for personal reasons.
So, first of all - the language packs for your Windows are irrelevant. The only language "packs" that you need to worry about are the language models that you download in the 'Translation' tab in the Configuration.
I suspect that you copied your Config from the Windows 11 machine to your Windows 10 machine but didn't download the English - Finnish model on your Windows 10. If that isn't the case, then my logical assumption is that your Windows 10 PC has very little RAM and thus the internal translator crashes due to that. Try turning off "Cache translations" and lowering CPU threads in the 'Translation' tab.
I'm glad you got it working with DeepL. And thank you very much for buying the app :)