On the same topic, Finland's neighbour, Estonia, has had online voting for over 10 years (since 2005).
https://e-estonia.com/solutions/e-governance/i-voting/
https://www.valimised.ee/en/internet-voting/internet-voting-...
https://e-estonia.com/solutions/e-governance/i-voting/
https://www.valimised.ee/en/internet-voting/internet-voting-...
Money quote: "What we found alarmed us. There were staggering gaps in procedural and operational security, and the architecture of the system leaves it open to cyberattacks from foreign powers, such as Russia. These attacks could alter votes or leave election outcomes in dispute. We have confirmed these attacks in our lab — they are real threats. We urgently recommend that Estonia discontinue use of the system."