I should take a closer look at Traveller, but when I read discussions about it, it feels like it might be more crunchy than what I'm looking for. If I had the free time, I'd like to kitbash something with Cortex prime, but I just don't have the time to do everything from scratch.
Traveller is many things... for some of us, Traveller == the Official Traveller Universe. Or some subset thereof (I personally reject the changes of the GURPS version to the setting).
For others, it's the specific edition
ruleset they homebrew settings for.
The core tropeset:
The Jump Drive: takes 7 days to go from point a to b; point b can be up to rating parsecs distance. Cannot be safely engaged within a gravity well.
6-guns in space: very few high-tech superweapons; the few that are present (plasma and fusion guns) have severe limitations.
Experienced PCs: Almost no fresh-faced 18yo characters; most will be in their 30's to 60's.
No FTL comms: No jumpspace radio. Interstellar comm is by sending couriers.
Technology progresses largely along a particular trajectory (hence, a single scale can be used)
Larger populations are less likely to have responsive government.
If you're looking for a solid "do anything sci-fi" - Traveller isn't it. Those tropes above are part of the core rules of all editions (excepting the GURPS and Hero ports, which lack the age factor.) It can do a lot, but there's little support for other tropesets.
Good entry points depend upon your needs - any edition supports the space trucker mode, most support the patron-hires-trouble-shooters well, Classic & TTNE have minis-games in parallel, while MegaTraveller has mass combat mechanics that play well and can handle asymmetric warfare easily. Mongoose's mass combat is in playtest.
Mongoose's recent rules update 2024 is probably the best start point for those wanting "currently supported" rules.
Most editions are able to convert on the fly... but running the same encounter in different systems can have very differing results.