All snap apps doesn't launch after Timeshift system restore

[Johny Beham]

Restored my system using Timeshift everything works ok except snap installed apps:
- Atom code editor
- Skype
- Slack
where among affected.

Reinstalling them didn't help even deleting files from snap cache, too

I've tried also
```
sudo snap refresh core --beta
```
didn't help as well.

Before reinstalling skype using Ubuntu software.
When launching app from terminal:
skype --secondary

results in:
internal error, please report: running "skype" failed: cannot find installed snap "skype" at revision 156: missing file /snap/skype/156/meta/snap.yaml

which might be the case with the rest of the apps.
After reinstalling still doesn't launch but command line:

skype --secondary

works.

The way snap works seems to be very sophisticated and fragile and installations can not be fixed with overwrite installs.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: snap (not installed)
ProcVersionSignature: Ubuntu 5.4.0-51.56~18.04.1-generic 5.4.65
Uname: Linux 5.4.0-51-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.16
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sun Oct 18 15:30:34 2020
InstallationDate: Installed on 2020-08-08 (70 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
SourcePackage: snap
UpgradeStatus: No upgrade log present (probably fresh install)

[Maciej Borzecki (maciek-borzecki)]

Please attach the output of the following commands:
- snap install
- systemctl list-units snap-*.mount
- losetup -l
- mount

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Lancillotto (antonio-petricca)]

Same for me on Ubuntu 22.04.

[Lancillotto (antonio-petricca)]

Could somebody tell me what is the flow to restore snap applications in order to try to provide a pull request for Timeshift project?