In the RX PMA setting of the Arria® 10 GX Transceiver Block, the CTLE Mode has "Manual" and "Triggered". How should I use them?

For Arria® 10 GX + Native PHY configuration, use CTLE : Manual and set any value in QSF or Assignment Editor. 
Also, as noted in the User Guide, CTLE : triggered mode is only available for Gen3 configurations in PCIe Protocol.

Arria® 10 Transceiver PHY User Guide 
https://docs.altera.com/r/docs/683617/21.1/arria-10-transceiver-phy-user-guide/high-gain-mode

(5.1.2.1.4. High Data Rate Mode for Continuous Time Linear Equalization (CTLE))

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Category: Transceivers 
Tools: Quartus® Prime 
Device: Arria® 10