Outlander very last episode, please explain!

[RipplePlease]

Just watched the grand finale of the whole series and I’m confused.
Jamie said he could never time travel/go through the stones but at the end there was a flashback (?) to the 1940s/50s of the first season. Claire is in the bathroom window and Jamie (in his period Scottish garb) is looking up at her from the street!?!
If he can’t time travel, how was he there?

He was dead and visiting her as a spirit, and remembering their lives together

Thanks.
I see.

If you go to this existing thread you will see there are any number of explanations.
https://www.mumsnet.com/talk/telly_addicts/5500746-outlander-series-8-the-last-one

Although interestingly no one has come up with the one suggested on this thread!