Great question!
I am generally seeing two schools of thought, Old vs. New.
The old school thought is .com all the way. Never deviate or stray from the .com.
The new school of thought is to use one keyword with an extension that works well with the keyword. We are seeing this used with startups, particularly in the crypto industry.
Which school is better?
At this time the old school is probably a safer bet, although things can potentially shift at anytime. That is not to say there can be some gems in the new school, it's just to say sales are fewer and farther between with new school.
One thing to note is you don't have to settle into only one school. You can go to both schools, although persecution can exist from the hardliners.