Finland’s parliament declared independence on Dec 6, 1917, after the Russian revolution.
This Finnish declaration of independence was recognised by Lenin at the end of 1917. [https://www.britannica.com/place/Finland/The-struggle-for-independence].
Finland was then ruled by its Parliament which had been established prior to the Russian revolution, and had been granted autonomy by Nicholas II in all respects except defence and foreign affairs.
This government existed up until July 1919 when Finland became a Republic.
I recommend that a new Ruling Authority ‘Parliament of Finland’ be created for the period of 6 Dec 1917 up until 25 July 1919 when the first President of Finland took office [https://blogs.loc.gov/law/2019/12/finlands-independence-day-and-the-finnish-constitution-of-1919/].