Hello,

Centos7, mariadb 10.4.7, row_format=Dynamic

INSTANT algorithm doesn't work if unique HASH index exist in table.

Also, all tables with unique HASH index have version=11 in 'Show table status'.
Tables without unique HASH index have version=10 and INSTANT alter work properly

How to reproduce:
1) CREATE TABLE `TEST` (
`ID` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
`MERCHANT_INTERFACE_ID` INT(10) UNSIGNED NOT NULL,
`ORDER_ID` VARCHAR(50) NOT NULL,

PRIMARY KEY (`ID`),
UNIQUE INDEX `PAYMENT_ORDER_ID` (`ORDER_ID`, `MERCHANT_INTERFACE_ID`) USING HASH
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB
AUTO_INCREMENT=1
;
2) SET SESSION alter_algorithm='INSTANT';
3) ALTER TABLE `TEST`
ADD COLUMN `test` INT NULL AFTER `ORDER_ID`;

/* SQL Error (1846): ALGORITHM=INSTANT is not supported. Reason: INPLACE ADD or DROP of virtual columns cannot be combined with other ALTER TABLE actions. Try ALGORITHM=COPY */