First thing that comes to mind is the nature of answers that fit such questions. In the absence of any technical solution (which OP had asked), it has to be a repository of known apps that cause this nuisance.
Secondly, this repository has to be a living repository , given that there would be a steady supply of new apps that would cause this lock screen behaviour.
In our framework , Community Wiki (CW) is a viable solution meeting these needs. What are "Community Wiki" posts? from mother meta is a useful reference. Here is what I propose:
Consolidate existing questions (two at the moment) by merging.
Convert the merged question into a CW (question and all answers will become CW posts).What is this lock screen with ads and how do I remove it? will be the foundation of CW.
There are comments in the main answer that list additional apps. These could be added as a CW answer to make the list comprehensive.
This CW becomes a canonical question for duplicate closure in future. In case OP (in future) finds their question marked as duplicate but they don't have any listed apps installed, it is not treated as duplicate (as is done for any other question, when existing solutions don't work).
In case, a technical solution emerges in future, that would also be included in the CW.
But wait and think
What is this lock screen with ads and how do I remove it? is a very popular question with about 250k views, with 60 votes on the question and the highest rated answer having 64 votes (It has 13 answers). It is unique in that sense and while I haven't verifed, it is easily the top voted (questions and answers put together) in the last two years.
By converting this to CW , none of the contributors lose reputation gained from it. Quoting from CW post of meta
But they will not gain/lose reputation in future, once it is made a CW
This could be a valid concern for the contributors. Unless, we have a community consensus on this it may cause resentment and one needs to be very deliberate about this.
So up vote if you agree and down vote if you don't.