I just installed GrapheneOS on a Pixel to test out - so far I like it and maybe a bit more than CalyxOS. Should run fine on a Pixel 6. Installation is easy, biggest headache was getting a fully unlocked phone. Meaning not only unlocked from any specific carrier but also unlocked so you can enable OEM unlocking (the bootloader). If you are buying used or refurb'd be aware than any phone that was previously tied to Verizon from a prior owner may be wiped and "unlocked" from a carrier perspective (i.e., you can pick whatever carrier you want) but it likely will not allow you to install a different OS, as Verizon locks the bootloader. To install GrapheneOS, CalyxOS or other systems to need to enable "OEM unlocking" on the phone and Verizon doesn't allow that. I had originally purchased a refurbished "unlocked" phone to play with but it was an old Verizon and the bootloader was locked. Returned it an paid cash for an unlocked new one from a retailer to ensure I could access the bootloader. Worked great.

There are a decent number of good tutorials and videos on GrapheneOS, but I followed the one linked below. Once you become familiar with the OS I'd also recommend watching a few of the "tips and tricks" videos on settings to enhance privacy. Also a number of good ones on Youtube.

Setup