There are tools, and tools, always remmeber that there are also people behind the tools. These guys are not many, but damn, they are creme-de-la-creme.... check them out https://www.linkedin.com/company/flowyteam/people

I trust the team as I have reviewed them quite consistently online.
Dirk shared https://www.g2.com/categories/objectives-and-key-results-okr
Yes, they are starting, but will grow fast; expected from a "high performer" on G2.
I am not even asking about the "free" version subscription for small teams. Their commitment to go get market adoption is not even considering small-term gains like many others around here.

What could go wrong from a "german thinking" ??
For me the core strengths of Flowyteam is not only the software, but mainly the knowledge behind.
Be aware of the OKR Institute https://okrinstitute.org/ the team handles; they are OKR trainers, they know the "thinking" as they live it on a regular bases. They preach it and build the app accordingly.

Many of us are consultants and we could further drive FlowyTeam App market penetration by becoming OKR experts. Many would like to even become affiliate partners... it is worth considering for long term business purpose. ;) The choice is yours, I have made mine.

PS May our paths cross in a special Sumolings OKR institute class of CERTIFIED OKR PROFESSIONALs (maybe Dirk and his team will surprise us further) Click on "helpful" if this resonates with you and see their reaction.