Please note I only "fixed" the issue caused by eager loading of entity types, eager loading of attributes with non-existent models always caused issues in the past as well (eg. deleting a module with a class that was used as custom attribute source_model or frontend/backend type model always caused issues in the past, removing those checks would be quite extensive and I at least prefer to be warned "early" of such issues).

Accidentally deleted all my VBox images and had no time to recreate.

Can't test it during next days.

@sven - I will make time these days to simulate your case. DDEV in my case requests only a couple of minutes to run an OM instance from scratch. I will install an extension then delete it from the file system. I should get your error, then I checkout this PR to see what happens. Do I need to take other steps to reproduce the issue?

@addison74 thanks. I know it takes only minutes to setup OM, but I've to do some more things. Need a new HDD, update my whole system from Win7 (do not laugh 😂), but the most important ... my beloved dog is 9y now and I just want to spend as much time as possible with her.

To reproduce ... install the extension you sent me and remove all files. No further steps.

It's much easier to simple insert a new entry into the eav_entity_type table with a non-existent model class.
(I did not actually install whatever extension caused the issue, because I don't have it but the exception clearly pointed to this. With the entity loading skipped it will also skip all attributes associated with that entity.)

I confirm this PR solves the issue reported here #3175.