litdb does include support for registering TypeConverters for mapping custom RDBMS types [1]. The drivers doesn't include any converters for custom RDBMS-specific types yet, but you should be able to register your own in your App or even better submit a PR to the postgres driver [2] so it'll work OOB (tho it'll be dependent on whatever postgres.js can be configured to support).
[1] https://litdb.dev/customize#type-converters
[2] https://github.com/litdb/postgres