sync for reddit crashed every time I opened it if play services are not installed (I am using an aosp android phone, grapheneos and lineages on a tablet) so it is kinda important that sync works without play services installed there is a better method for device attestation https://grapheneos.org/articles/attestation-compatibility-guide
I know this is an old post, but i wanted to chime in and say i would love to see Sync available for de-googled phones. I will pay like everyone else.
It works on my grapheneos device!
although there is no option to pay and remove ads without play services, you can just directly pay him on patreon and use an adblocker