In 10.5.8, do this:

CREATE OR REPLACE TABLE _test1 (num INT);

CREATE OR REPLACE TABLE _test2 (num INT);

INSERT INTO `_test1` SET `num` = (SELECT `table_rows` FROM `information_schema`.`tables` WHERE `table_name`='_test2');

The last statement returns "SQL Error (1406): Data too long for column 'TABLE_SCHEMA' at row 1".
It did work fine in 10.4.8.
On 10.4.17, the same sequence returns either the same error or "ERROR 1242 (21000): Subquery returns more than 1 row" (which is wrong, the subquery on its own returns exactly one row). Which of these error messages i get seems to depend on the user.

I got the error message about "more than 1 row" on 10.5.8 when trying

INSERT INTO `_test1` SET `num` = (SELECT `version` FROM `information_schema`.`tables` WHERE `table_name`='_test2');

Other similar queries also fail:

INSERT INTO `_test1` SET `num` = (SELECT `maxlen` FROM `information_schema`.`character_sets` WHERE `default_collate_name`='ascii_general_ci');

INSERT INTO `_test1` SET `num` = (SELECT COUNT(*) FROM `information_schema`.`system_variables`);

It seems like this occurs with any non-empty table from information_schema, both Memory and Aria. I never saw that from any other database.