2.2 is introducing plugins, which can extend type mappings and method/member translations from outside EF Core. I'm currently porting Npgsql's own plugin model (introduced in 2.1) to the new EF Core one (npgsql/efcore.pg#658), and one missing extension point is for EvaluatableExpressionFilter: our NodaTime plugin flags SystemClock.Instance.GetCurrentInstance() as non-evaluatable, to make sure it's evaluated at the server (much like DateTime.Now).

It seems important for this to make it into 2.2, otherwise NodaTime specifically won't be portable to the new plugin model (and this may also affect other plugins). I'll probably be able to submit a PR in about 2-3 weeks, is that early enough?