I encounter the same issue, and apparently we are not the only ones:
- https://xdaforums.com/t/rom-unofficial-12-s-lineageos-19-1-for-z5c-suzuran.4417131/post-89665514
- https://old.reddit.com/r/CalyxOS/comments/1bpsnbg/feeld_login_not_working_email_link_login_via/
- FEELD Login not working (Email link login via Firebase) (#2252) · Issues · CalyxOS / calyxos · GitLab
- App incompatibility due to not installing sandboxed Google Play - GrapheneOS Discussion Forum
- https://beehaw.org/post/16622495
Reaching out to the Feeld support team might be the best option, or filing an issue on the microg github