If it works from host abra-ka-da-bra.mydomain.com command, but does not from Cloudron - isn't it something specific to Cloudron implementation?

Is there something I can grab and share with you next time I will encounter that?

I tried to check the code, kindly references by girish, but I realized it's a task for a few hours at least, as the logic depends on the provider.

There is a thing I'm not sure I follow: why requesting A record anyway? You just need to ensure the DNS entry is resolve-able, without getting under the hood - it feels like braking the abstraction level here, unless I'm missing something, for sure.

From the code it seems like I was kind of right then - you specifically check an existence of A record, instead of if the entry could be resolved.

Let me illustrate that the following example:
A entry with * pointing to smth

will lead to the following command to succeed:

host anything-at-all.domain.com

but the following command to fail:

host -t A anything-at-all.domain.com

Because anything-at-all entry doesn't exist. But it will be resolved, thanks to wildcard entry.

Please, let me know if you believe I might be missing something here.

if that's not too much to ask, may I ask you for the code snippet? I will think of the ways to see where it might not work or when I miss something (with the later more probable, I would say).

you don't need to know if A record is there, you are verifying if name could be resolved.

This is what it does currently With wildcard provider, in fact, there is no way to check if there is a real A record. You can only check if the DNS resolves.