I think ATTiny with Blynk would be very useful since ATTiny is used in very many projects.
However, There is no way we could use blynk with ATTiny. We need ATTiny support.(the only connection options would be hc08/hm10/esp8266/esp32 like modules that could be used with ATTiny tho)
Why do you think, they are not supported? Just try it, at your own risk and peril, and then tell if it doesn’t work)
P.S. There’s actually an example for ATtiny85 serial