Error converting psql to mariadb: QuoteHelper.php line 62: Only strings, Literals and Parameters are allowed

Nextcloud version (eg, 20.0.5): 21.0
Operating system and version (eg, Ubuntu 20.04): MacOS Big Sur
Apache or nginx version (eg, Apache 2.4.25): 2.4.46
PHP version (eg, 7.4): 7.4.15

The issue you are facing:
When I convert DB (in this case: from Postgresql to MariaDB) I get error message In QuoteHelper.php line 62: Only strings, Literals and Parameters are allowed

Is this the first time you’ve seen this error? (Y/N): Y

Steps to replicate it:

php occ db:convert-type --clear-schema mysql <myuser> 127.0.0.1 <mydb>

What is the database password?
Clearing schema in new database
Creating schema in new database
The following tables will not be converted:
oc_audioplayer_genre
...
oc_retention
oc_users_external
Please note that tables belonging to available but currently not installed apps
can be included by specifying the --all-apps option.
Continue with the conversion (y/n)? [n] y
oc_accounts
 0/2 [>---------------------------]   0%
In QuoteHelper.php line 62:

  Only strings, Literals and Parameters are allowed

Stack trace shows that instance of Doctrine\DBAL\Schema\Column is passed to quoteColumnName($string).

As quick workaround I added to QuoteHelper.php (line 57):

if ($string instanceof \Doctrine\DBAL\Schema\Column) {
    return $string->getName();
}