Any idea of when a stable release might be available?
So to be clear, we’re talking about migration procedure between pretty old TOS 3 to contemporary turris OS 5. Let me correct my statement above - I was first unsure what kind of upgrade do you mean.
I personally do not expect significant effort is going to be spent to improve migration scripts - so I think wait for some rainy afternoon, and after full backup of your device performing the fresh install of current release could be the RightWay™.
Or, you can check the status of the migration procedure here, Migration from 3.x to 5.x (#344) · Issues · Turris / Turris OS / Turris OS packages · GitLab, compare missing features with your personal setup, and decide yourself if you’d like to make a try, (or even better, try to improve the scripts! )
Personally I went with the fresh install. as from my experience, to deploy the proper config is often faster than trying to fix system being in broken or undefined state.