You can use this list to determine which instance blocks the least instances (BI close to zero), and at the same time, blocked by the least number of instances (BB close to zero).

A value of BI close to zero that may indicate that the instance admins use defederation as a last resort. At the same time, a value of BB close to zero could indicate a trusted instance. You can then inspect the instance’s instances page (such as this one for lemm.ee) to see which instances it blocks.

There’s also this tool that shows you which instances are federated or blocked from one another.

I say after all that though, that lemm.ee is a good place. However, sh.itjust.works is notable among the larger instances to refrain from blocking any instances.