For me support is when they actually make/port games to it. Call it whatever you want, it's a form of support in the end.
What would be perfect, as the Switch is now, is for it to get ports that can actually run on the system like MK11 and Outer Worlds as good examples.. Oh and Alien:Isolation looks so great I might have to get a new SD card since it wont get a physical release. But, as mentioned, games like RDR2 or Anthm or CP don't stand a chance to run on Switch... So, make original games for it. Octopath did pretty good I heard. Bayonetta 2 sold better on Switch than on Wii U (DUH) and I am sure BAyonetta 3 will do great too. Actually, it seems Astral Chain did pretty good too.
And if the system continues to sell as good, it it should get more support/parity/a helping hand/3rd party voodoo magic/whatevs and might live through 2021 even.
Bottom line: The Switch is selling darn good and third partes should pay attention to that...
P.S: I still don't understand why there sis no GTA5 port on Switch... That just baffles me.