There appears to be an issue with 10.3.34 where the number of parameters that can be used within "IN ()" is limited to 999. If you have 999 or less, the prepared statement will work. As soon as there are 1000 or more, the prepared statement stops working. I can not find any error that gets flagged or returned (I might need to do some more digging) but it seems to silently fail.
The raw sql that is produced by the prepared statement that contains 1000 or more parameters does work when used directly in the database though.
I have tested the following MariaDB versions with 1000 or more prepared parameters.
10.3.27 - works
10.3.31 - works
10.3.34 - fails.