[unregistereddev]

Any investor can. If the option is not available to you, contact your brokerage to ask about it. Many (most?) brokerages require signing a waiver confirming that you understand the additional risk posed by trading in low-volume pre- and post-market yours.

[MuffinFlavored]

Is it typically behind extra fees?

[yareally]

Other than the fees that normally come with trading an ETF, no. Commissions vary by brokers though. No fees are related to the time you trade though