Yea post links on Lemmy are unfortunately really hard to deal with. There are discussions on how to fix it
The current workarounds seem to be
- use an app or browser extension to handle the link for you
- link the instance and tell people to look for the post
- use a third party service to generate instance agnostic links
I use the first option for myself (Boost on mobile, InstanceAssistant on Desktop), but we really need a better solution