Using lambdas as callback functions
As @timemage explains in a comment, you cannot pass a capturing lambda
to a function that expects a plain pointer to function. There is,
however, a way out of this: the Ticker class provides an overload of
the attach() method that allows you to provide a parameter of any type
to tour callback:
template&lt;typename TArg&gt;
void attach(float seconds, void (*callback)(TArg), TArg arg)

You can use this version of attach() and provide it both

a non-capturing lambda that gets a pointer to systemManager
that pointer as a third argument.

Edit: I did a few tests, and it seems my compiler cannot properly
perform template argument deduction in this case, but the approach works
if you explicitly specialize the template. Namely:
tickerSystemManager.attach&lt;typeof systemManager&gt;(
    1000,
    [](typeof systemManager p){ p-&gt;sync(); },
    systemManager);