This isn’t specific to Linux necessarily, but the best free fonts I like the most that I always install regardless of OS are:

• DejaVu (included by default in a lot of Linux distros but not in Windows)
• EB Garamond (a font intended to replicate Garamond but with the Open Font License)
• Inconsolata (a font intended to replicate Consolas but with the Open Font License)
• Noto (also included by default on a lot of Linuxes but not on Windows)
• Vollkorn