You can pretty easily use the SWADE rules + the sci-fi companion to to a solar punk game. I’m running a western / sci-fi mashup right now and loving it.
The last parsec is a setting for SWADE with campaigns etc.
I’ve also looked around for sci-fi campaigns, so here are some systems that I’ve heard about but never tried myself:
Traveler Orbital Blues
And of course starfinder, from Paizo. Pathfinder 2e is imho the best ttrpg rules system out there, and starfinder 2e is pretty new, with some adventure paths already published.
i run a SWADE game, and the book indexes are great. Nothing online, but various VTT systems can be used as a database if you buy the content.
The SWADE rules are considerably simpler than D&D, and they have optional rules that you can mix-and-match to fit the mechanics better to your setting. For example, expanded fear and insanity rules for horror campaigns, or armor ranks for a sci-fi settings with mechs and spaceships, etc. It’s especially fast in the combat department, I recently had a boss fight that lasted 2 rounds (took about 20 min IRL) because two players rolled well.
Cypher is great too, perhaps even better, but Cypher really requires an experienced GM. The rules are so general that you as the GM really need to decide for each roll what the modifiers should be, there’s guidance but no specific systems for grappling, chases, overland travel, searching, nothing. So it can be really good and fluid and creative if you can pull it off as a GM (and the GM never rolls anything, giving you more time & energy to focus on your GM role), but an inexperienced GM will suffer.
Also consider games powered by the following system:
<edit> Ah I see you have it in the list, I’m referring to PbtA.
They are VERY rules-light, very roleplay-heavy, but fun. I’ve been a player in a *Monster of the Week" game for years, and it has been a blast.