Before the recs I just want to shout out libro.FM - they sell audiobooks and donate half of the profits to independent book stores.

Classic sci fi:

• The dispossessed - also the left hand of darkness (which is meant to be good buy Inhavent read)
• Foundation series
• permutation city

I think the more modern sci fi is good too so I will give you some recommendations anyway:

• Project Hail Mary - mentioned by other commenters, really good
• Children of time - first and best of a series, really good
• Expanse - series of books set in the near future, hard sci fi and a bit of space opera
• Red rising - a space opera a bit like a fantasy book in a sci fi setting
• Murderbot - series with a bit more more comed, very entertaining and easy to get into

sailfish?