You are correct, PHP and MySQL are the only system requirements but it is not possible to predict how those resources are managed. From your responses it appears the database table may be changing the encrypted password when it is stored so I would rule out any browser dependence.
Please check and see (in phpMyAdmin) what the Collation value is for the password field (table lr_v32_users).
To check if the encrypted password is being stored correctly, go to the LiteRadius admin control panel and change the password to "testuser". It's encrypted value in the lr_v32_users table should be:
$1$sF.eDEau$klMehV06sJdpRewYe338A.
. Is this the value stored in the lr_v32_users table after the change is made?
You have also claimed that updating password field manually in lr_v32_users table does not preserve the password. To verify use a utility like phpMyAdmin update the password field with
$1$sF.eDEau$klMehV06sJdpRewYe338A. (password: "testuser")
. Update the field then review the password. Is it the same or has it been altered? You should be able to update the password field with
$1$sF.eDEau$klMehV06sJdpRewYe338A.
then login with the "testuser" as password.