Handling Null values (and equivalents) routinely in Python
Generally I don't think you should have a class for this functionality. There's no state and no particular meaning to MyUtils object here. You can make this into a long function in whatever module you deem appropriate in your codebase.

I think this function as written is a code smell. It 1) doesn't cover a whole lot of types and 2) implies that where you're using it you're not going to have even a rough idea of what type of data you're expecting. In most cases you will have some idea, and even then it's not usually a good idea to do explicit type checking.

Where you're using this for numbers you can replace it with myval if myval is not None else mydefault.

A function like this may be more useful for strings, for which there are a wider range of essentially empty values. Perhaps something like this

def safe_string(s, default="", blacklist=["None"]):
    if s is None or len(s.strip()) == 0:
        return default
    if s.upper() in [b.upper() for b in blacklist]:
        return default
    return s