Restore OH 3.4 Full-Backup on fresh OH 4.x Openhabian Installation?

to migrate from current OH 3.4.3 to OH 4.x, i consider doing a fresh Openhabian installation to also have the latest OS underneath.
But I wonder if it’s supported to restore the OH 3.4 Full Backup on a OH 4.x installation ? the Full Backup also contains add-ons. but aren’t the add-ons outdated ? or will OH 4 automatically update all add-ons after Backup has been restored? any other things to consider/worry about ?
appreciate any tips and tricks on this.

It should working.
Please read twice or more what is the different in OH3.x to OH4.0x from the migration guide and release notes, and reserve a lot of time for doing the migration.
Normal you get all the official new binding.
Old unofficial binding which you installed by hand, will stay, and perhaps working…

Officially it’s not supported, as any modifications that are applied during the update process would be lost (e.g. new / different jaon structure, default config changes, etc).

If you want to have a fresh installation and change from v3.4 to v4 I would:

  1. Install a fresh v3.4
  2. Restore the backup
  3. Upgrade to v4

See OH4 fresh install and restore OH3.4 data

It might work but is not guaranteed to.