Any Free Sci-Fi OSR recommendations? Preferably friendly for players with 0 experience in TTRPG games.

Hello! I am a new GM with 0 experience in DM'ng. I finally gathered a possible group of players who are also new to TTRPG games and I asked if they wanted Fantasy or Sci-fi. The result was (albeit a lil' bit sadly), sci-fi.

I did some searching and asking around and was recommended Lancer TTRPG. Got hyped of it's concept and tools along with it free. Only did I realize the free was for the players and not the GM TAT.

Sadly I don't have a Paypal or credit card (for the time being) even if I am willing to pay so paid games are off the table for now...

So far I've gotten the option of studying either:

Esper Genesis 5E Sci-fi (free quick starter)

or

Stars without a number.

Haven't checked them yet fully, will review them later. Hoping for your advice on this matter! Thank you :D

Also wondering, since we are now in the topic of sci-fi. I found the fantasy genre to be 10x easier to set up and prep due to it's amount of resources and tutorials whereas I find sci-fi to be fewer in number. Any advice on how I can GM and prep a sci-fi oneshot (which may turn to a campaign) with knowledge on how tos with fantasy?