pin ubuntu version

[jackkav]

aiming to fix #7867

blockers
node-libcurl is built using ubuntu-latest and therefore a different glibc version so cli tests fail
playwright seems to fail with ubuntu 20.04 getting first window

may be abandoned unless we can find a stronger reason to pursue further

actions

• build node-libcurl with ubuntu 20
• fix the app.firstWindow() playwright issue

[filfreire]

fyi if we do this, we also need to downgrade snapcraft's base on electron-builder config. Downgrading that brought it's own set of problems (see #5555)

side-note, for taking the other route (prepping for ubuntu 24), some things that need to be fixed first on electron-builder side:

• allow for core24 https://snapcraft.io/core24
• allow for different gnome plug https://github.com/electron-userland/electron-builder/blob/15ce5b4164378f7398ff84cabe8ee97eef5cfd1b/packages/app-builder-lib/templates/snap/snapcraft.yaml#L133C1-L136C38