Open is good, but it just means we have a chance to check how the sausage is made. It’s no inherent guarantee against bad ingredients in the recipe.
Which is a different issue than the OS itself. Some browsers/plugins let you excercise more control over data collection; operating systems not so much.
Based on measurements made by a community member:
…and the research of Douglas Leith & al at the Trinity College in Dublin, I’d prefer SailfishOS over Lineage any day. From their October 2021 report:
We find that the Samsung, Xiaomi, Huawei and Realme
Android variants all transmit a substantial volume of data
to the OS developer (i.e. Samsung etc) and to third-party
parties <…> (including Google, Microsoft, Heytap, LinkedIn,
Facebook).
LineageOS sends similar volumes of data to Google
as these proprietary Android variants, but we do not
observe the LineageOS developers themselves collecting
data <…>
Notably, /e/OS sends no information to Google or other
third parties and sends essentially no information to the
/e/OS developers.
https://www.scss.tcd.ie/doug.leith/Android_privacy_report.pdf
There’s also the eye-opening March 2021 report: