Situation
As seen here, the builds have been failing at some point after the commit: feat(fix-code): Add comments for Jet framework.

Probable cause
Current error message
error: Server does not allow request for unadvertised object 8553a4a0a72ac7c81ae7a59dc0380902208f73cb Fetched in submodule path 'Libraries/tinyobj', but it did not contain 8553a4a0a72ac7c81ae7a59dc0380902208f73cb. Direct fetching of that commit failed. ##[error]Git submodule update failed with exit code: 1
indicates that there are problems when fetching 'tinyobj'. After inspecting a similar case, I suspect that the submodule 'depth' (as of right now, 2) might be too small for fetching the specific commit for 'tinyobj'.

git -c http.https://github.com.extraheader="AUTHORIZATION: basic ***" submodule update --init --force --depth=**2**

Extra
Here' another related issue: AppImage/AppImageKit#511