Cf. this comment by Mark on an answer from that (different) question "Can I install two setups of the same major version on the same box?"

Note that Jose's answer applies to Windows install... The unix (e.g. Linux) install allows you to install SQL Anywhere in any directory and therefore you can install multiple copies of the same version (or any version) on the same host.

So, yes, you should be fine with parallel installs of v12 and v16.

FWIW, it's also contained in the documentation's FAQ page:

Can I install and run two different versions of SQL Anywhere on the same computer?

Yes, you can install multiple major versions of SQL Anywhere on the same computer. For example, SQL Anywhere 9.0.2, 10.0.1, 11.0.1, and 12.0.1 can all be installed and run independently.

However, you must use caution when starting a SQL Anywhere executable that has the same name in multiple versions (for example, dbisql or dbinit) to ensure that you are starting the correct version of the application. You can either specify the full absolute path using environment variables such as SQLANY16, or ensure the version of SQL Anywhere you want is specified first in your path.

Note, if you are about to use both versions in parallel regularly (say, running larger databases in productional usage), both database server instances will compete for the machine's resources, so you might have to specify reasonable cache sizes for both.