Language of TMs that accept some x in less than 50 steps. Is it in co-RE?
Maybe that will help ?

https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-045j-automata-computability-and-complexity-spring-2011/lecture-notes/MIT6_045JS11_lec09.pdf

Page 42
Credits : Nancy Lynch MIT

Applications of Rice’s Theorem

• Example 3: Another property that isn’t a language property and is decidable

{ M |M is a TM that runs for at most 37 steps on input 01 }

– Not a language property, not a property of a machine’s structure.

– Rice doesn’t apply.

– Obviously decidable, since, given the TM description, we can just simulate it for 37 steps.