Oh man, I am sorry to say, but this will not work for you. The EarMix 16M is part of the "ecosystem" of the Series III mixers, which is using AVB II. There is no chance to get AVB I and AVB III to communicate. As a former owner of RM32AI | RM16AI | CS18AI, I honestly can only recommend to get a 32R. It's a complete different world with much more options than the AI family will ever have (even though representatives of PreSonus are still talking about "future updates" in the closed Facebook groups).
To answer your question: The EarMix does not "see" linked channels. It receives a signal routed to AVB channel 1, AVB channel 2, AVB channel 3... Then you have the option to link inputs (odd/even) on the EarMix itself. It doesn't matter if the routed signals are input channels, flex mixes, effect returns/subgroups or functional channels (talkback, Aux Ins etc.).
19 input channels are 3 too much for the EarMix, so you need to use submixes. There should always be two channels (linked) reserved for effects and functional things like talkback. Everything about this theme is explained in the above mentioned thread in the Live Sound Forum. Use the labels to understand the explanations. Or you let me know what your 19 channels are and who wants / needs to hear what, then I can present a concept of how to use one or several EarMixers.